I've logged my fair share of miles with a cargo trailer, first time with the truck camper out back. I figure the compressor is just smart, no need to ride around with all that air in the bags if we decide to unload the camper. I can't know I'll always be near air so it's peace of mind really.
I've heard there are 0-2" lift 5100s and 4-6" lift 5100s. Since I'm thinking of doing a 1" zero rate add a leaf (glorified block) a 0-2" lift shock would be perfect. According to their website, the 5100 has "digressive valving". Maybe I should give that a google and see if I can debunk it.
