I have an idea for the adjustability w/o the steel plate (which is $260).
Made the seat pedestal from aircraft plywood and put fixed rollers on the bottom.
Make another box attached to the game (where the attachment struts were) that nests inside the pedestal base like an upside down dresser drawer.
Slot the inner box and use a
star knob on top of the outer box (between your legs, just in front of the seat) to lock them together.
Install a trampoline spring inside the nested boxes. Loosen, push back to the desired distance, tighten.