Might be referring to some other design of power valve. If one actually has one in hand, looks at these power valves with the spring on or removed like I’ve shown in the video, you see the plunger, or valve, all extend open and seat the same. No different than the height of a spring retainer installed on a valve and the spring pocket on a head. You remove the spring and replace it with a slightly stiffer spring of same od and height. Open/closed overall travel has not changed. Hope that clears it up for some. So, there is no changing it’s range of travel from open/closed. All that’s being done or proposed is an incremental spring rate change. Finding a spring that’ll work is the possible fly in the ointment here.