I agree! Find another installer! We have a Gl1800/Hannigan conversion which we had done at their factory in Murray, KY. They NEVER said anything to us about not using reverse! My husband is the driver, and he tries not to over use his reverse, but there are some situations where it would be impossible to get going any other way. I couldn't push it, that's for sure!
I've been reading this message board for over a year now, since before we got our bike triked, and I've never seen anyone mention not using reverse, no matter which conversion.
Course, this is just my opinion. Perhaps you should check with some other installers and ask that specific question.
Good luck!
Jo Anne