pete air trac air ride question

anyoe got an old pete air trac on there truck, wanted to see if you could tell me if the chassis rails on your truck are below or above the rear tires? don't need a measurement just an eyeball

im running low profile 285/7524.5

 

well I just went out and changed the ride height arm going to the valve as it was old and banged up, I had bought a new kit for $8 well I set the chassis at the same height as the top of the tire, just about 2" almost taken out the back end, well long story short just took her for a spin up to 80mph on the freeway and this truck rides smoother then any of my other newer trucks ive had, no shakes it had a terrible vibration bobtail going up thru 70-75mph that you would have to just let off of throttle cuase it was really bad. now it didn't even shimmy one bit the whole way up to 80mph bobtail.it even got rid of shakes on deceleration and a bad axle jump when I was braking on decel I mean this is crazy. I read how to do it the correct way and it left my truck way to high just like it was before I decided to this and from bottom of frame to axle tube centerline I was getting 11.5" which was what the peter air trac specs called for but it didn't show for what size tires which made me think how Is the tire size not figured into the ride height equation that all the sites with HIEGHT ADJUSTMENT PROCEDURE say nothing about tire size and height which do matter. my truck originaly came with 11r24.5 and it has low pros so that figure cant be the same. so now after my adjustment with top of tire to top of chassis I got 9 3/4" from bottom of chassis to axle tube centerline . truck looks even now no more angled rake as well and air bags don't look overinflated.