Update:
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I was wondering why everyone else with rhino ramps were having no problems putting their cars on the ramps, but my rhino ramps were shooting all over the place.
By taking 4 2X8 x 8'' or 2X10's x 8' (2 each side) and supporting them with a couple bricks or blocks you can extend the length of the approach and thus decrease the incline. This will decrease the tendency to puch the ramps and at the same time provide more clearance for your car undercarriage.