Here is a picture of the seat to brake pedal 19 inches, the seat is all the way back but it's hitting the bracket for my seat belt it will go back a few more inches with the bracket moved.
If that is the shoulder harness in the photo, the driver of that rig is going to crush their spine in a rollover. The shoulder harness should be on a crossbar at shoulder level or slightly above to avoid spine compression in a roll.
Just an FYI.
Dan