bottom perch is what oem is. there was a lot of conversation many years ago stating ford tested the shocks on mid perch, but due to the headlight height regulations from dot, it was set to bottom perch. when ford came out with the torsen front diff, it did/does not play well with your axle angle. 2010 and 2011 really didnt have a problem, but from 12-14 the torsen made the difference. lot of binding in 4wd and torn boots along with busted axles. boots are pretty easy to replace, however ford doesnt sell just the boot, you have to buy the entire axle. i have replaced several boots over the years due to crap i run over while im offroad. takes time, but not hard. i think the aftermarket shocks put the truckheight around mid perch so there shouldnt be any adjustments needed if at all possible