I used JB Weld on my Mystery Helmet.
I dabbed it on and kind of slid it up and down to work the resin smooth and flat.
I screwed the right top ear piece on in case I ever want to change RF's
That's what I did.
Hope this helps.
I used Goop, that is found at any hardware store and some small philip head scews. So I glued it down and used some rubber ended C-clamps to hold it down tight and put the scews in from the inside. Small enough not to poke through. I just pre-drilled the holes in the helmet and marked the location on the ear parts and started a small hole there for the screw to go in. Seems to hold just fine.