The roof rack on my Impreza Outback does not seem adjustable? This doesnt make much sense to me...It has two screws in each side of rack bars going into the rails. When attempting to remove these screws they just turn in their place. Judging from the rubber trim peices along the rails, Subaru does not intend for the rack to be able to move along the rails to adjust for larger or smaller items to be attatched up there. My owners manual does not include a section on the rack. Any help please ? I want to add a bike rack but need to lengthen the span of the bars front to back. Thanks.

Nope, they are not adjustable.

The screws are attached to nuts that are set into the rails. The nuts have a really bad habit of rusting and breaking off so that when you try to unscrew it it just turns in place. I think it's happened to pretty much every OBS owner that has tried to remove them after a couple of years. I used to have a Thule rack on mine and I was only able to get one screw out successfully so I ended up having both the factory and Thule crossbars up, which caused an annoying whistling sound if I didn't use the fairing.

The way people have been removing them is to take the whole assemly off, crossbars and rails, then drill out the screws or otherwise remove them. It does get them off but the problem is that you won't be able to get them back on again.