I looked into doing custom tees for my front end swap, the material wasn't going to be grossly expensive, but the machining would be if you can't do it yourself. Just so we're all straight though, you want GSXR-1000 Trees that emulate the CB750 stock offset and height, so the geometry emulates stock?
Just wondering why you're headed this direction, lock to lock a little tight? Weird turn in? or are you just looking for that cb750 feel with a nicer ride?
I know mine is tight lock to lock, i actually moved the tank back about 2 inches to make it all work. Pretty happy with the result, turn in is fine, cruises straight with hands off the bars, haven't pushed deep into too many corners yet though.
Good luck with the setup! Love your bike, paint job, spokes, wrap, everything!!! Definitely one of my inspirations, kind of ended in a different direction though.
Jon