RE: what expoxy GLUE?
Depends on how fast you want to get in the air. I know many use the fast setting epoxy. Use it sparingly as it adds weight.
I met someone who uses weldbond to glue his foam back together. He claimed that he found that the foam would break right next to a previous epoxy repair. The Weldbond, he claimed, has more flex to it so reacts a bit more like the original material and won't break next to an "epoxy line". Takes longer to dry though.