andy,
i bet me and my girl could fit on your seat no problem. my frame stops where the wedges on the bottom meet the shock mounts (i moved the one that ties the tops together forward) with my stock seat on she knows she can't go further back than the shocks and we never have a problem. were both pretty skinney though (i'm 5'7" and 140, shes 5'4" and about 95)
-andrew