Not completely sure where this should go..
My wife, in winter, rides one of those very upright bikes (some variety of Trek Navigator, to be exact) with the riding position angled so her feet can reach the ground or the pedals at extension. This means that most of her weight is on the seat. We haven't had much luck finding how to keep the seat from sliding down into the frame, though; it's tight and I don't want to mess the seatpost up. What do you suggest?