RE: Using carpet as a backstop?
At our outdoor 3D Practice range we use the large wood frame with carpet on the front and back streched tight and filled inbetween the carpet we fill it with shrink wrap, we havent had to replace the shrink wrap in over 8 years, we just recarpet the front and back twice a year, we have over 140 members shooting them alot and these work very, very well for shooting field points at.
Do some dumpster diving at the local carpet stores and youll find all the carpet you need and visit the dumpsters at larger manufacturer plants , or dept stores such as home dept etc to get your fill of dissgarded shrink wrap.
Deborah