my rear support is basicly a "cheese wedge" of closed cell foam covered in clothits 9"wx12"L and thickness tapers from 2 to 5 inches, I use this because if I set the 9-13" bipod in the third notch I can slide the rear support to shoot from level to the top of most ridges here, saves me valueable time setting up the shot. here is a pic, IIRC that deer was taken at 702 yards

RR