Actually, Cab, I've been running the 9x30 on 10" from the get-go. Where things have changed is the new convertor leaves a solid .05 better in the 60', but is slower from the 330 on. It appears that it locks up tighter than the old convertor did, and my little torque-challenged 360 just can't pull as hard because of it. Given that, as these tires are plumb wore out I'm thinking that going to a 28" tire would help give me more effective gear for the entire length of the track. I wasn't sure that 10's work with 9x28's, but if there are people running 12's on 9x30's I should be okay. The old convertor was a TCS 4-4200, the new one has about 500 rpm more stall. The change on the launch was like night and day, but it sure slowed the car down, overall.