Pics would help as I can’t quite understand what you mean. So, guessing a bit here….
On the 591 you can slacken off some allen bolts on the underneath of the clamp assembly (the bit with winder), which allows you to slide it along the length of the ‘gutter’. You may just need to move it back a bit so the clamp arm isn’t so far forward that your bike is too forward on the gutter.
Edit – the same allen bolts allow you to remove the clamp assembly altogether too, and let you turn it round, which you might want to do if you’ve got more than one on the roof. If you do swap it round tho, watch out for your chainring making contact with the clamp arm – it will eat it! Simply put the chain up onto the biggest ring and no problem.