I'm 5'9" with a 31" inseam, my pedals are set at the furthest location and I have a 1" spacer on the steering wheel.
With this set up it is the most comfortable I have ever been in any car ever.
5 hours without a break is no problem and no numb bum either.
I doubt very much weather you will need any form of booster cushion on the backrest.
