I have used epoxy on an almost daily basis in the past. Not all epoxies are created equal. The thickness of the layer will matter as to how hot it gets.
We almost always had small amounts left over in the dixie cups we used to mixed the resin and catalyst. The left over got hot enough to melt the wax on the cup.
Although I have never used any on foam, based on my use of epoxies in other applications, I would do a small test. Better safe than sorry.
HANDLING PRECAUTIONS:.............................................................Avoid all skin and eye contact. Wash thoroughly after handling. Launder contaminated clothing before reuse. Avoid inhalation of vapors from heated product. Precautionary steps should be taken when curing product in large quantities. When mixed with epoxy curing agents this product causes an exothermic, which in large masses, can produce enough heat to damage or ignite surrounding materials and emit fumes and vapors that vary widely in composition and toxicity.
This is from an MSDS for epoxy. I realize it states," In large quantities", but I don't know where melting of foam is on the chart compared with ignition of other random materials.
But, also keep in mind this is coming from someone who has paid workers comp and general liability insurance premiums for many years.
Epoxy paint may be the way to go as a preventative measure with new nucs.
Alex