Lifting does not increase travel. In fact it diminishes it.
Lifting by using longer springs and dampers is what I have in mind. I've raced quite a bit in Baja and off-road endurance. It takes a while to setup a suspension right and I'm by no mean an expert but I've given enough feedback and been involved in setup a few times to get a good idea of the recipe and nothing serious can be done without at least two scales. That increases the speed of iterations dramatically.
One of the engineers told me once that you have to be freaking good or lucky to setup your suspension well without balancing the car, particularly if the level matters (for esthetic or aerodynamics)
So I can have an idea of how much skills and knowledge you might have put in your truck to get it setup well, most people tend to underestimate how tough it is to do it right.
I don't have the equipment and my expectation with my humvees is low to be honest so I won't change my setup at least until I get more serious into off-road, but I can appreciate the value and potential challenges.
I saw your posts about springs, did you change the dampers?