I think I did it! I glued a piece of 3/4" plywood to the bottom to eliminate the bottom flexing. I re-cushioned the "inner bottom ramp", replaced the weatherstripping, and got an 8' section of 2.5" hose. I then modified the 2.5-1.25" adapter to make it sloped inside instead of stepped (to prevent bee-bashing). Now I have various lengths of 1.25" hose to attach to the box, then an 8' section of 2.5" hose with another adapter on the end so I can change tips as needed to suck up the bees. It seems to work great now. No more screaming, no more leaks, and plenty of suction! I have a removal scheduled for Friday the 31st, so I'll get to try it then. I also got a digital inspection camera (finally) that I can try out. Boy, am I psyched!
Thanks everyone for your tips!