What psi would be good for a 13x8x22 MT drag slick? I went to the test + tune last night but only got a few runs in. I started at 19,lbs and got down as far as 17,lbs. best 60ft was 1.98. How low should I go? I was actually slower on the 1/4 by .01 Just want to be ahead of the game for next time so not wasting time. Thx.