I'll make sure my design can accept a small spring for the check valve.... although I might try it without.... Maybe if I set it up with just a few thou travel it might grab right away without bleeding back....

I will be custom cutting the slot, so I'll look at making it just barely long enough to clear the linkage with the thought to incorporating your self-valving O-ring design.... Give a though to any headspace saving changes and let me know....

Bob