Why do all the instructions for a 2" spacer say to keep the isolator, but the 3" says to not reuse the isolator? Wouldn't the 3" lift only get you 2 1/2" of lift without the isolator? Can I keep the isolator with the 3" spacer for a true 3" of lift?

99 Sportage 2Dr, 1.5" body lift, 30x9.50 Cooper M/T's, high lift, CB, custom bumpers, Warn manual hubs, Tom Tom GPS, snorkel.
99 Jeep Cherokee 3" lift, 31" mud terrains