A big can of unused epoxy finishing filler, a leftover from painting the Jeanneau, had been staring at me for a year or so.
Light weight finishing filler is not intended to be used for structural (gluing) applications but I decided to do some experiments anyway. Without any surface preparation and just using a single fillet on one side I glued together scrap pieces of MDF, marine plywood and foam.
The pictures show that even a light weight finishing filler is stronger than these materials. The materials fail before the fillet.