Roller Valve Spring vs FT Valve Spring

Do you know the inner spring seat height (the one with the .755 diameter) of the retainers? If you can come up with that, I can find out what a set of Melling VS-2203 springs (.745 I.D. .900 O.D. & 1.77 free length) or equivalent added as an inner spring would add to your seat and open pressures and what locator it would need to shim it up with. The downside is it’s about a $100 upgrade, and there’s possibly a set of springs available for less than that. But a different set of springs is probably going to require a different set of retainers, so it still may be the lowest cost option. Shimming would be the lowest cost option, by far.