I wish I understood your post better.... So far, I'm not convinced that the "bumper" on the back of the valve in my .25 cal Disco is doing any good.... The adjustable hammer travel / valve lift is likewise questionable.... From what I can gather so far, having the most hammer travel you can get allows the least hammer spring preload, and hence easier cocking.... It also allows you to vent more pressure because of the increased hammer energy/momentum....

The added hammer travel is a good thing if you need more hammer strike.... Once the hammer strikes the bumper on the back of the valve, however, it prevents any further self-regulation, and the velocity of the shot string immediately plummets.... This does NOT appear to be what is happening with the bstaley O-ring mod.... so I'm left to assume that the resilience of the O-rings is working to "round off" the top of the shot string.... However, I've never tried it, so that's just a guess....

Bob