It sounds like you are just a little bruised up. I manufacture a rib protecting seat called DeepSeat. Same principle as the Ribtect, just a little different shape. Anyway, we produce our seats with the trim removable so you can trim your seat to fit you better. Many people trim off an inch or more from the top of our seats to make them more comfortable. Our trim just slide back on then.
In any case, it sounds like your seat is just plain too big, and I would highly recommend a good quality ribvest.