Stiffer springs don't help much when it comes to bottoming out, setting the spring tension mostly raises or lowers the ride height.

Here is what you can do keep from bottoming out:

-Thicker shock oil
-More Droop (move your shocks to the lower holes in your shock towers, this will give some buggies more droop if their shocks were the limiting factor)
-Use shock pistons with smaller holes.


A combination of the above should fix your problem.