The threads look great, have to be careful when starting to screw in initially, but works like a charm!
I may get an adapter to put in between so I don't have to screw/unscrew every time. I would hate to cross thread even once!
Being the first guy with a threaded output on a RD your feedback is much appreciated. In retrospect I guess it would have been better if I had made a female threaded output for you, this way you could use a small metal pipe nipple between your RD and the ball valve, so you could leave the nipple threaded into your RD and thread out the pipe part from the ball valve.
I just got done designing my first couple of female threaded output caps for the RD3, haven't printed/tested any of them yet, but I see no reason they shouldn't work out like the male threads I've printed so far....