The seats in the Gazelle, although far better than the 206, have a steel top to them which protrudes further out than the seat foam does and sticks right in to your spine between the shoulders.
I can only assume that before being compressed through years of use, the foam would've been alot thicker!
At least the Gazelle seats are adjustable fore and aft, which isn't bad for an old type, not many others do!