I tried contacting Marty a couple of times but had no reply.
I have one of his 2 button bell cranks, which I got from another forumite. It's beautifully made but the bell crank doesn't turn on the bushing, which I'm told is normal. However, I don't know of a way to mount it securely in a 1/4" thick wing without leaving enough slop so it can turn. So, I pretty much have given up finishing my model.