You can go as low as 100 psi, and as high is 200 psi on the nitrogen. But it's best to stick with the 150 psi. The nitrogen does hardly anything to the dampening. It's mostly to keep the oil from cavitating, or getting air bubbles in it which makes the dampening ineffective. To add more rebound,, you can add another large shim to your valve stack. Go to the Fox website, and look for their valving chart. Let me know if you find it, if not I can post it up when I get home. It shows the different thicknesses of shims, and they give them a number. Like all. 010=70#, .012=90#,etc. It also shows how doubling and even tripling the large shims will affect the valving.