It's a delicate balance, to be sure. I suggest you consult with your EPDM supplier for assistance. Uniroyal used to have a nice tech service center with an extrusion/hot air/microwave line where they'd fine-tune curing and foaming of EPDM compounds. That product line is now owned by Lion Copolymer, and, if you're using their EPDM, I'm sure they could be of assistance.
