Well, so far, I think I'm the only one who has Bilsteins and the AC lift installed (??), and I only installed my shocks late last night, so I can't tell you everything, but I do know this (this is where I have to stop being quite so nice to AC...)
AC is using Rancho 9188's with their lift kit...Rancho recommends 9156's with theirs. Both of these shocks have an extended length of 12.45" IIRC...(stock shocks are 11.5" long extended.) The Bilsteins are 12.46 or 12.48" long (can't remember right now), so in other words, they are the same length as the shocks that Rancho and AC recommend with their lift kits. I honestly think the reason AC isn't recommending them is they don't know the specs of the Bilstein product.
I also measured the distance from eye to eye with my a-arm at full droop (resting on the bumpstop w/ no shock installed) when I was putting it in, and it looked like the a-arms got me another inch at the bumpstop, so I think it all adds up well...one inch more travel at the bumpstop == roughly one inch more travel at the shock == (approx) a little more than two inches of additional downtravel.
Mosi might be able to chime in on this issue as well.