I'm confused here, when the valves are closing, the springs are pushing them closed with very little pressure exerted on the lifters. That's when they load up again so, on the next stroke, they pump oil up through the push rod. When you set lifter preload, you're setting them at partial compression to facilitate the proper pumping of the hydraulic lifter. The seat pressure doesn't change with the same valve springs whether you have .400" or .600" lift. You just need more pressure at max lift at higher RPMs so, the valves don't float when going over the top of the cam lobe.As you up the psi it over comes the ability of the lifter to stay pumped up.
Hydraulic lifters are pumps, they need to collapse and pump up or, no to hardly any oil will reach the top end. Solid lifter lash is set to act like hydraulic ones so they can pump oil up to the top too, thus the tappet noise from them. It's not how much lift you have, it's how many revs you run. I can run .540" lift @ over 5400 RPM with these springs and keep a fairly low seat pressure.
You must be registered for see images attach