I"m a little shorter and lighter than you, but also use a 143 mm saddle. The pads of some bib shorts are too small for me, and resulted in me sitting on the edge of the pad stitching...it resulted in cutting my tush. I think you need to check your seat height and position, perhaps it is too high resulting in rocking motion on the saddle, and try different shorts...perhaps the seam in the pad is in the wrong place for you...