So you can’t use polystyrene resin with XPS foam either?
No polyurethane resin will eat it up.
Alright good to know, thanks 
Thanks for your input mat! I’ll definitely blend it with polystyrene even though you are making me reconsider it! What are the odds of crossthreading these brass nuts though? They seem pretty tough to me! Plus, the thread that will form in the epoxy might reduce the stress on the nut a little bit haha 