I am stunned to hear of problems with Falcon Floats. Never anything but rave reviews before.
I am also a BIG proponent of Urethane glue. I think it will help with the problems described. Scuff the mounting surfaces with some 80-grit, dampen them, and use Gorilla Glue to bond everything together. You can glue directly to styrofoam. Lighter than epoxy, stronger than whatever it's stuck to, and chemically compatible with everything I can name. (waterproof/fuelproof).

Spreader bars are not there to spread, they should more precisely be called anti-spreader bars.

I am also a big proponent of foam-core floats. I tooled up to make my own after being unable to get BJ floats anymore. Ralph (seaplane) makes very similar floats and sells them for much less than I could. Niagara, RnZ, FoamFloats.com are other places to get foamies.