You may need 3/16" thick foam but start with 1/8 SC41 durometer material. I've also used a cut-to-fit section of vinyl mat that the battery sets on that reduces wear from vibration. To aid removing the battery I made straps out of a length of 1" web material (cut from a ratchet clamp) with sewn loops on the ends that go around and under the battery to 'lift' the battery from the hole.Don't forget we need seals under the battery and fuel system covers. I think they are the same so only one piece tooling. I don't deal with these materials very often, I was looking for black 1/8" closed cell foam if there is something better please share. It has to be compliant enough to mold around the pop threads or whatever those things are called.