Hot wire cut and the surface of some extruded polystyrene is not always a good surface to bond to.  It may need sanding which will be tricky with 1/8"  Not a big deal for a model, but worth doing some tests if you are going to bend it.  Also check your epoxy does not have solvents in it which attack polystyrene.   On the bright side, you can make pretty good panels with polystyrene by heating the surface so that the bubbles are dispersed and you have a solid polystyrene surface.