With my PRG shackles set at the lowest hole, they brought my 3" Alcans (which sagged to about 2.25") up to 3.25". Later on, when I Titan-swapped, I moved the shackles to the highest hole to get the rear to just over 4" of lift.
Yeah, that first trip with the Alcans (from that thread) sagged a lot. But honestly after putting the shackles on and getting that additional height, I can't remember a time after that where I sagged significantly. It was almost like the shackles "fixed" the weight capacity thing. What "probably" was happening was that since I had the additional height/rake, the sagging just wasn't as noticeable. Idk. There was no real solution.
I fixed it later by getting a new pack with more height and capacity... lol (4" with 500# over stock)
If I were you I would get the PRG (not nisstec) shackles and try them out. They are much beefier and easier to use than stock. They should hold up longer and in tougher conditions. That might satisfy your height needs.