Bumpstop lengths are going to be vehicle specific for the most part. On the ACOS the overall length is longer than the OE bumpstop and the rubber end on the ACOS shaft makes a great bumpstop and I've tested it lots.. I'm at 4in lift including the ACOS on 31's and no fender trimming with no probs. I would suggest maybe some prothane inserts in the coils if there where any questions about it not being long enough for say a taller lift etc..

 

Cool beans that was like my last worry

 

With ACOS, if you need more bumpstop in the front you need to add to the bottom, not to the top. This way you can set exactly the amount of bumostop that you need/want.