I originally planned on using a battery box / strap for the cranking battery but immediately changed my mind when i saw much the box moves regardless of how tight you strap that sucker down.
New epoxy plug time.
1st drill pilot holes followed by a forstner bit.
since my foam comes up pretty much to the bottom of the deck, i cut an oversized piece of closed cell foam:
compress it and push it down (I used a punch):
wet the sides of the holes with epoxy:
Add filler (colloidal silica is usually preferred) until it's creamy peanut butter consistancy...tiny bit of reflow.
Put the epoxy/filler mixture into a sandwich baggie and snip off the corner:
fill the plug holes from the bottom-up:
^^^ check in every once and awhile to see if there are any leaks...just keep topping off the plug if it does until it starts to solidify.
fasten the battery hold-down...rock solid now.