If like me, having spent all your beer tokens on the car / are a tight git (delete as appropriate) and need a roof rack - this seems to be a cheap solution without compromising on safety.
If you look on the usual auction/collection sites, you should be able to lay your hands on a brand new unwanted Q5 rack for only a few tokens. There seems to be a surplus of these as I understand they come free with a Q5.
Tools wise you will need:
<ul>[*]Drill and bits[*]Angle grinder[*]5mm allen/hex key[*]tape measure/ruler[*]pencil[*]knife (to cut rubber strip)[*]optional extra - label machine to mark up each foot.[/list]
Points to note: <ul>[*]the rails on the Q3 are not parallel[*]one roof bar is shorter than the other![*]you are going to need to remove the foot with the 3 pegs on it, remove 2 of the 3 pegs, and shorten the bar by 10cm, drill and refit the foot.[*]It appears that the integrity of the foot is largely maintained by the grip around the outside of the car rail, so the pin is more of a guide to line everything up and even with only 1 pin doing the job its not going to fail. If you wish you can add in a new pin if you feel such inclined, but it will take some precision drilling and lining up of a new pin.
[/list]
The first task is easy as the shorter rack which is the Q5 rearmost rack will fit straight on the front of the Q3. The only thing that you will need to do is slacken off and re-tighten the 2x hex bolts holding each foot to the rail to allow everything to line up with the rails and fit snugly. All the holes in the bars and the feet are elongated to allow this adjustment.
Next you need to do some extreme moding!
As you will know - there are 2 pins on your Q3 to receive the rack/foot. You will need to make it look like the top one in the pic here.

FYI, if you want the measurements - here you go

The foot comes to pieces very easily - just remove the 2x hex bolts from the top of the rail and it will all fall off in your hands. The plastic casing is held together with friction and there doesn't appear to be any clips holding it as it is held together when bolted on the bar.

As you will see, the bolts go through one bracket to another to spread the load. This is bit fiddly to get back together, so note which way up everything is as you take them out.
Now break out the angle grinder/massacre tool and grind off the 2 pins that are closer together.

As you will see, i slipped and caught the pin that i needed to leave behind.
As i took off a little of the plastic coating, I wrapped a bit of electricians tape around the bracket and cut out the tape around the pin so that i had a plastic coated finish to touch the car rail. (No pic).
Re-assemble the foot without the plastic casing and fit it to the car (do not fit to the bar yet).
Now fit the Bar which still has the other foot to the other side of the car and rest it on your newly farkled foot. This will allow you to mark the roof bar to see where you need to cut. In these pics the bar is just resting on the foot and is not attached.

Here is mine all marked up and ready for cutting and drilling

As you can see i needed to take 10cm off.
Take care with re drilling the holes as these need to be dead center to fit in the groove on the top of the rail. Whilst i did miss a little, my error was quickly covered up when I later fitted the rubber on the bar.
Remember you will need to cut the roof bar at the same angle so that the plastic end fits on.
Then all you need to do is re-assemble the foot and casing and fit to the bar.
I found that i needed to release the hex bolts again to get the feet to sit tightly against the car rails. Then I just tightened these up, got the label machine out to make sure that I fit everything the same way around. That way I shouldn't need to adjust them again.

Now all you need to do is remove your newly fitted bars and install the rubber into the groove of them. I found that I needed to take them inside and warm everything (including me) and rub a bit of washing up liquid on the rail to get the rubber to fit properly.
Job done.
If you look on the usual auction/collection sites, you should be able to lay your hands on a brand new unwanted Q5 rack for only a few tokens. There seems to be a surplus of these as I understand they come free with a Q5.
Tools wise you will need:
<ul>[*]Drill and bits[*]Angle grinder[*]5mm allen/hex key[*]tape measure/ruler[*]pencil[*]knife (to cut rubber strip)[*]optional extra - label machine to mark up each foot.[/list]
Points to note: <ul>[*]the rails on the Q3 are not parallel[*]one roof bar is shorter than the other![*]you are going to need to remove the foot with the 3 pegs on it, remove 2 of the 3 pegs, and shorten the bar by 10cm, drill and refit the foot.[*]It appears that the integrity of the foot is largely maintained by the grip around the outside of the car rail, so the pin is more of a guide to line everything up and even with only 1 pin doing the job its not going to fail. If you wish you can add in a new pin if you feel such inclined, but it will take some precision drilling and lining up of a new pin.
[/list]

The first task is easy as the shorter rack which is the Q5 rearmost rack will fit straight on the front of the Q3. The only thing that you will need to do is slacken off and re-tighten the 2x hex bolts holding each foot to the rail to allow everything to line up with the rails and fit snugly. All the holes in the bars and the feet are elongated to allow this adjustment.
Next you need to do some extreme moding!
As you will know - there are 2 pins on your Q3 to receive the rack/foot. You will need to make it look like the top one in the pic here.

FYI, if you want the measurements - here you go


The foot comes to pieces very easily - just remove the 2x hex bolts from the top of the rail and it will all fall off in your hands. The plastic casing is held together with friction and there doesn't appear to be any clips holding it as it is held together when bolted on the bar.

As you will see, the bolts go through one bracket to another to spread the load. This is bit fiddly to get back together, so note which way up everything is as you take them out.
Now break out the angle grinder/massacre tool and grind off the 2 pins that are closer together.

As you will see, i slipped and caught the pin that i needed to leave behind.
As i took off a little of the plastic coating, I wrapped a bit of electricians tape around the bracket and cut out the tape around the pin so that i had a plastic coated finish to touch the car rail. (No pic).
Re-assemble the foot without the plastic casing and fit it to the car (do not fit to the bar yet).
Now fit the Bar which still has the other foot to the other side of the car and rest it on your newly farkled foot. This will allow you to mark the roof bar to see where you need to cut. In these pics the bar is just resting on the foot and is not attached.


Here is mine all marked up and ready for cutting and drilling

As you can see i needed to take 10cm off.
Take care with re drilling the holes as these need to be dead center to fit in the groove on the top of the rail. Whilst i did miss a little, my error was quickly covered up when I later fitted the rubber on the bar.
Remember you will need to cut the roof bar at the same angle so that the plastic end fits on.
Then all you need to do is re-assemble the foot and casing and fit to the bar.
I found that i needed to release the hex bolts again to get the feet to sit tightly against the car rails. Then I just tightened these up, got the label machine out to make sure that I fit everything the same way around. That way I shouldn't need to adjust them again.

Now all you need to do is remove your newly fitted bars and install the rubber into the groove of them. I found that I needed to take them inside and warm everything (including me) and rub a bit of washing up liquid on the rail to get the rubber to fit properly.
Job done.