Inferno ST-RR: Question on the Hardness of shock Springs

Hello everyone.
Just a quick question. I am trying to set up my shocks. At the moment I am using the #600 oil and the blue springs (medium). I have noticed that during acceleration the back end dives to the point of almost touching the ground (maybe it does, not sure), yet I have no issues with the car being too wobbly.
I thought of using harder springs or a higher grade oil, but I am not sure which one is the way to go. Should I go with medium springs and #800 oil or #600 with the harder springs (red)? I am told that most of the work in the shocks is performed from the oil rather the springs but I am not sure to which extend.
Cheers!