So you want to split the wing in the center?
I did that with some fiberglass tubes and rods for this build:
Big Blu 96 KFm9 glider - http://www.rcgroups.com/forums/showthread.php?t=1470211
That was made using a thinner foam, 6mm thick +/-, so I was a able to put the tubes between two layer of foam. The glue used as polyurethane or PU glue named Gorilla Quick. That glue foam up when it is wetted so it fills all the voids, joins the tubes and the foam, and spreads the strength over a wide area. You can see that in that thread.
Where are you home ported? What part of the world. Some of these materials may be harder to get in other places. The place where got them is listed in that thread above.