>> Starting line beams are suppose to be 5/8 " off the ground.
The spec is 1-5/8", not 5/8". Although I swear that Mason-Dixon's were that low at one time!
I went the other way, a number of years ago when bracket racing at Quaker City Raceway, which had a crazy loose rollout. Went from 26" to 23" fronts, and only picked up about .015 in reaction time, much to my surprise.
Myron doesn't believe in the law of dimishing returns.
This is a guy that changes from 48psi to 50psi and tells me it changed his light.
That being said, you have to watch out for not only the tire diameter/circumference, but also the construction of the tire. Street type radials, street bias-plys, and drag frontrunners may all react differently to tire pressure changes. It may be worth some time to do some static measuring, comparing pressure changes.