Can you provide any details of how you filled the wings with poly-foam?
Sorry for the late reply.
I used quality poly foam, a friend gave it to me.
It says on the cylinder that it will expand only 2x after you have put it in and that is reasonably true.
I do not think its possible with the other cheap stuff I can buy here in Holland. That goes ballistic after you put it in for up to an hour or even longer! You need the quality type of it I think.
Anyways. I made about 8 square over the length of the wing, about 1x1 inch the Peter Sripol way. Have the knife in a 45° angle when you cut.
You can then glue the pieces you removed really nice back in later. The idea was to have the holes relief the pressure when the foam expands and that worked well.
For this big wing it totally did the job. Without the foam it would be too flimsy. Now it is really tough!
Cheers
P.S. It also works nice in your tail section when you have too much torque.