Pipe Lift Survey

I read everywhere that 1 1/2" spacers give 2" of lift, and they are more popular than 2" spacers because some guys think that would be too much. I went ahead and installed 2" pipe couplers that were actually a tad taller, at like 2 1/8" (had to get em bored out a little, to fit around the shock tube). Anyway, I got a total lift of only about 1 1/2", so what's up with that?

Ok, whatever, my main question is this: Of all you guys that have pipe/shock spacers, where do you run your preload settings? I had them all cranked up tight before the project, and since the installation they are all on the lowest setting. It obviously rides way stiffer than before the mod, as you all know, but I could get probably another 3/4" lift by cranking them all the way back up. Do I dare do this? Can a guy put too much preload on a spring? Would it ride like a friggin wagon? Thanks for all the input.