My new treb may have a complex hacked together unstable trigger system, but it works. I clamped the axle to the work bench and spin the arm around. Even the sling holder and new sling configuration seems to work great. Now I just need full length sling sling lines, a firing pin, and the upper part of the frame.
Now, I think it will work. I always can confidence in the concept, but my implementation of it has left me wondering it it would actually work. Maybe as soon as next week I will be able to get some real throws off.