Thank you for the info, Subscriber! You made some very good points that I will ponder & look into more closely for sure. Greatly appreciated!
Also, I suggest you make the effective compression volume adjustable. This will make life easier; should you decide the cocking effort needs to be reduced; or could be higher. Now, you could adjust the compression volume in a number of ways, but here is one way: The image below is of my Baikal MP-46M SSP pistol. It has the ability to adjust the piston's "TDC" distance from the "cylinder head" in 0.25 mm increments, via a little grub screw positioned in one of four windows in the threaded piston hinge base.
My hillbilly way isn't near as elegant or effective...
Pump rod will be threaded through block that secondary link arms attach to & the end of rod is drilled/tapped for a 5/16-18 set screw held in place with red Loctite or retaining compound. Then I could just insert an Allen key in end of pump rod & adjust "piston TDC" as needed without tearing everything apart. Another set screw in bottom of block would lock rod in place.
If a full stroke & ~2500psi turns out to be too much for components...or me... I was thinking that I could simply place a "locking collar" of sorts on the pump rod (think drill bit collar/stop) that would limit how far I could open pump arms, thus reducing final pressure yet still be consistent.
Just thoughts right now though.