Stock suspension help

[PoWn3d_0704]

I am looking for a way to soften my ride on the dunes. I am currently running the stock 450r shocks and A-arms.
I weigh about 150-155 lbs and the bike seems to want to buck me off when running across tracks and such on the flats.

This is how I basically have the suspension setup currently.
The shock preload has about 3 threads above the top of the top locking ring, and all of my compression and rebound settings are at 20 (just to see the effect)

I dont really understand what does what and how it affects the overall handling of my quad.
AND, how the rear shock messes with how the front suspension handles.

some info would be appreciated. I also did some measurements on unloaded travel, resting travel, and loaded travel of the bike. I just measured from the ground to a center point on the frame in each instance.

Thank you all so much.