Foam Tac is great stuff. But I still use the old standby, Beacon 3-in-1 Advanced Craft Glue (this is the stuff Yardbirdz used to sell as "Ultimate Foam Glue"). It's $5.99 for a 4oz bottle (twice as big as Foam Tac, and a bigger 8oz bottle can be found at some places for $9.99), available at all craft stores like Michael's, Jo-Ann's and Hobby Lobby, and I always use at least a 40% off coupon.
I think the only difference between Foam Tac and 3-in-1 is that Foam Tac has less ,or no, acetone in the mixture. Me, I like the acetone to create that "weld" bond on foam. I even sell it at my booth whenever I go to shows.