If I'm not mistaking bottoming out is due more to the lack of dampening in the shock itself. The spring rate determines how quickly the vehicle returns to normal ride height after compression. Springs will also determine body roll as well. It would take a whole lot of spring rate to compensate for a shock not producing enough dampening to the point that it would keep the suspension at full extension and not compress. I would recommend trying different shocks with HIGHER dampening rate. I'm no expert but I was a professional R/C off road racer for 15 years and did lots of testing of suspension LOL. Someone correct me if I'm wrong.