I'll see if I can find something in the info I had from doing the rear speaker kit - obviously there is constant power supplied to the radio (or else you'd need to recode the security key each time it was powered on
). You should be easily able to route the power down from there.
On the epoxy topic, be sure to test it on one of the scraps you've cut off to be sure it won't just eat all the way through your now precious work!