RE: anything wrong with carpenters glue for joining wings?
I once had a stabilizer that was glued on with carpenter's glue pop off in flight. This was in normal flight, right after takeoff. I inferred from this that carpenter's glue tends to be a little brittle when dry. If so, vibration could cause it to crack.
That was with the original Titebond. There are newer formulas, which may be better. And it only happened once. But once is enough. I use epoxy for this now (as well as for wing joining and firewall attachment).