Georg,
As you can see I've done this mod on two different Rockets without any difficulty. As I said I run the Avon Cobra front in the 150 and have had my bike to 126 mph by the gps with no problem......
You did trim down the "boss" on the rear of each fork leg, correct???? If I recall I took about 1/2 inch (about 12.5 mm) off. This is the only way I can see that there might be the potential for the fender rubbing. Where is the tire close to the fender?
Hope this helps, I'll try and go get some better pictures tomorrow.
Lonnie