I have spring retainers, rear sway bar and a rear locker.
I guess I will run with the 4"up and 6" down for now. I was just wondering if anyone had played around with their rover travel.
Engineering a solution with no requirements is a waste of money. The big questions are - best for what? How do you use the truck? What kind of load do you normally have? Do you have corner weights loaded and unloaded? Is it a trail truck? Or do you need to have a need to go faster in rougher terrain? 4" of up travel might work fine at one valving but not another, depending on the weight of the rig and how fast you drive. Or if the terrain has a lot of rock shelfs that bottom out the suspension. There are too many factors to consider before just picking something out of thin air to decide what works "best".
Once you have an answer to some of those questions, the next step requires access to a car lift, a forklift (or both), or at the very least a ramp of some kind. What you want to do is to remove the shocks and then cycle the suspension at each each corner independently, taking measurements under full articulation. Once you have that as a baseline, then figure out what you want the shocks to do for you and go from there, adjusting check straps, mount points, shock length, shock valving, and last but not least, bump-stops and bump-stop type all to suit.
If you don't want to go through all that ... I think it's better to fit OME's and not worry about it
They have engineered a solution that works well at a wide range of conditions. Trying to re-engineer that solution on your own is not a trivial effort. Arriving with a final setup that has the same performance, durability, and low ongoing maintenance costs is not cost competitive in my opinion. If you need to deviate from an OME or factory spec shock to specialize the suspension for some purpose, we'd need to know what that purpose is.
cheers,
-ike