I really like Bill Kitto's three part M6 trigger mechanism, and I just ordered one for my next gun build. In corresponding with him, I learned that he now offers it with a spring resetting line release. His release uses a tension spring recessed in a slot on the outside of the gun, as shown in his pictures below.
I kind of like my own torsion spring release, but I just thought I would mention it as an option for anyone interested.