Just wondering if any of you have seen any replacement seats for the GTR? My wifes finding the back uncomfortable. She says the cut off at the back limits the amount she can slide back and the dip in the seat causes her to sit forward. (if you look at it the seat actually cuts off at a real angle rather than 90% making it effectively a lot shorter) than it could be Ideally she wants a flatter seat which goes right to the back of the frame. Any thoughts?