I have only made a mild attempt to try and get more clearance between my guide seals and retainers on my J heads.
With +.075" retainers, mine show a minimum of .570" clearance and the taller retainer is not the issue, my issue is that the locks stick down about .06" lower than the retainer. So my minimum clearance is between the top of the seal to the bottom of the locks.
With lower guide seals or taller valves, I can see getting into the .600" lift range.

EDIT: Since the fourth lock groove is sticking down past the retainer by .06", I trimmed off the last groove off of my locks. The three remaining grooves are in full contact inside of the +.075" retainers. This gave me an additional .06" clearance from the top of the guide seal to the bottom of the +.075" retainer. I now show .61" to .63" clearance after this modification.
Note: My spring pressures are only #310 at max lift.

Even with the above modifications, this just gets enough clearance for lifts in the .530"-.550" range pending how much clearance you use. Much more lift on my setup would require longer valves.