Update:

I tried several things...................

I went to wallmart and bought the triple expanding foam. Bought two cans. Supposed to fill up an apple size box right? WRONG! Did not even fill up a third of the box. So I pissed away $11. on that one. Then I bought a 4 ft by 8 ft sheet of R10 insulation foam, cut it into 2ft by 2ft strips and glued them together. This one works good with BH' s and FT. The FT are pretty hard to pull out. I can tell from the way it performed that shooting BH' s into this thing that it will not hold up long. So I guess I am still looking for the ultimate home made BH target.

Thanks for all the suggestions!