Interesting comments about the problems with the SmoothStop - I have used 8 or 9 and every one has been great. I set my linkages and airlines up per BVM instructions and have never had a leak. I do maintain mine once a season (pull plunger, change O ring, lube and re-assemble).

I just used the last one of a batch of three I bought at a big discount from an unhappy user and they have worked fine as well.

The parking brake "feature" of the mechanical valves (UP acts the same) is very nice, especially when working with the model on a short table.

Barry