I glassed right over the foam on my Byron F-16.
I believe the foam used there was the injection foam, very tight with the surface sealed no pores I used 1 oz cloth with Z poxy finish resin, then vacuume bagged.
It worked very well only minor pin holes, only one application of epoxy.
The parts are very strong and withstand all kinds of hangar rash. They are also very light. The whole plane weighs in at 11 3/4 lbs.
I have tried it over other foam products aand not been very succesful it just soaks up lots of epoxy.

Hope this helps Don B