I'm in love with mine - but I weigh 145 soaking wet. Funny, I would have imagined you guys to be well padded. I guess though, if you don't fit into my jeans why would you fit in my seat.
One thing on the backrest - especially if you're heavy: Mine is attached really solidly courtesy of Dinqua and some fender washers. Seems to me if it weren't fastened well it would wobble and eventually something would break. The seat is basically plastic after all.