Helping a buddy out with a DOHC 750 that was running funny. I found lots of vacuum leaks at the boots. The carbs weight, now solely on the front boots was enough, with time and bumps to sag and oval out the boots some. When I went to wiggle the carbs the rack just popped out.
I put it back together, adding some bailing wire over the frame and onto some of the screws for some strain relief. It's ugly, but helped.
I guess the lesson is, if you eliminate the airbox, find some way to support the back of the carbs.