Okay, some are going to call BS on me, and say it is not possible, BUT here is MY personal experience, take it for what its worth.
I have a 3 in CF and the Old Man Emu 881's. I was told I was not getting 4 - 4.5 inches of lift out of them even though it seems I would, I was told that my shocks keep that from happening. Mine BTW are KYB. Now I recently got the All Pro rear leafs which lift 3 inches and I was told to go to stock shackles so I'd sit correctly as I like the stock stance of the rear a bit higher. So I did. It was lower in the rear. I put back on my 1.5 lift Downey and the truck sits about level, not the stock preferred stance. That would seems to indicate to me that I am getting 4 - 4.5 in of lift in the front. So as said before take it for what its' worth, I can only tell you what I've experienced.