I'm not sure if you want this but it is a little tutorial I did on using Gorill Glue to fill gaps in foam.
If you want to use it then there you go - and - if not just let me know and I'll delete the post! LOL!!
Although this little video is about filling in a foam ding I wish I had video'ed the slicing open of the E-Flite AT-6 wing center section and subsequent filling of the grids with GG in the same manner to strengthen it. That might have been the one you would have wanted. I may be able to do one along those lines still though as I have a "old timer" that was given to me with a crushed tail plane so I will look into repairing it in the same manner and see if that can be done. If I do I will let you know.