I dont know if you guys shoot bow and arrow at all.  The bow and arrow target styrofoam type material I found seems to work the best.  Its durable enough to have an arrow tip go through it and not produce that big of a hole most are self healing.  It works great for this type of stuff.  Im actually experimenting with making a cutting mat out of this stuff.  The problem is getting a thin evenly cut layer big enough and flat enough to produce the idear im looking for.