i'll give a review of the coldsteel i bought
i got it a few months ago when they first were offered. i emailed the guy when i recieved it and he offered to refund my money, but i never got around to sending it back. none of the surfaces were 'flat'..either convex on the bottom or concave on the sides, both in the center portion of the reciever. the top bends, i would'nt call them rails, were of different height by about .050 if i remember correct. and when i squeezed the front trunnion in with a vice, it spread the top out a good half inch on either side, being to narrow in the front, the rear trunnion fit ok. the only thing i liked about it was it was made from thick stock, i was going to not bother with the center support.
this is merely a review, not a flame. perhaps the later versions have the bugs worked out