RE: What do you think of FORMOST 150 ?
(Any) balsa wing construction is so weak that it would be practically impossible to control or limit the foam expansion.
Even for the fiberglass tailbooms, I was lucky I had some good idea what to expect, but some modelers had already a bad experience trying the same... injecting more than I did... with the expected result... [:@] Better to do something like this with a plywood reinforcement...
And glassing the wings is not enough, if the internal structure fails...
Nicolas.