I think I wont try the foam board. Just to risky after looking at fire tests on you tube. I think I will just use a 1/2" thick piece of wool to cover the entire table when needed. I got some samples for another project from this company and I think I can get a yard that is 72" wide for about $136.00. My table is 60x30, so I should have some left over for maybe a small pressing mat...LOL
www.sutherlandfelt.com
This is the sample they sent me. I just tested it with my iron and it worked great.
Felt Materials - SAE Pressed Wool Felt - F-7 SAE Wool Felt, Gray - The Felt Company