I concur wholeheartedly with the Jetronics / UP6 suggestion.

I used to have a bunch of Smoothstops, just because that's what came with BVM kits. I got fed up with the fact that they would work fine for a while and then suddenly leak like crazy, requiring hours of fiddling and going back & forth thru the instructions to no avail. To me, the Smoothstop is kinda the RAM 500 of brake valves - works sometimes, not others, and figuring out why it suddenly became unhappy involves hours of frustration. Conversely, something like a UP6 is the Jetcat 120 of brake valves ... it just plain works, and works, and works, without constant fiddling.

Gordon