I wanted to create the comfort of an office chair.
This is the setup I finally came up with. A top case is necessary.
The sleeping bag is a huge one with a 3" diameter heavy cardboard cylinder inserted at its center to prevent future sag. It's held on by 2 bungee cords.
The two gel pads in one cover at front has the bottom pad doubled over at the front to create a lean-back effect and also to prevent one from sliding forward while riding.
I can ride all day with no aches or pains whatsoever.
I made the bottom seat cushion previously for my height.
Total cost around $60.