well you could raise the ride height. its gonna take away some suspension travel as far as articulation and handling goes, but it should eliminate the bottoming out.

and a thicker shock oil will actually stop the bottoming out more than springs. springs control ride height, but generally speaking when your talking about absorbing impact, its the piston being force through the oil that is actually providing most of the resistance. the spring is just there to say how fast the truck will return to equilibrium.

unfortunatly with thicker oil, lets say your driving across the grass, or worse, a gravel or rock area. the suspension will be less likely to absorb the impact, and pass more of the impact through to the chassis; end up bouncing around instead of the suspension absorbing the bumps.