Crosman 1377 flat top diy?

Picked up this old American classic for 15 bucks the other day. Some fresh seals and a quick printed ldc and it is a great shooting pistol. Stacking premiers at 5 yards. Dose anyone have a drawing for a flat top piston conversion on these. I may fire up the lathe and make one if I can find a working design. Thanks!
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i have a kit somewhere in my stuff but my point will be this has been done a dozen ways
1 Oring, 2 Oring, a solid head, full length with no adjustment, adjustment with both end sort of equal in length, just a head with and Oring and you can see that in pictures online but i would think without the valve you are maybe wasting your time
and adjustable piston head seem to be the best idea
One or two Oring piston head i think you will find makes little difference i would put a wiper on it somewhere
so, this is a game of either buy or do your own R&D