I built mine on a Stiller Predator and am more than satisfied with it.
Mike Bryant did the work and it is superb. I used the stiller on his recommendation. Mike builds precision rifles for a living and one of his rifles set the 600 yard BR world record, so he knows his craft. I have shot other custom actioned rifles (Nesika and Borden) and they are very nice too, but based on my sample of one, I can't see them being any better than the predator.
John