... a 172cm tall driver, with a helmet on, is going to pass the CAMS 50mm helmet to rollbar regulation
Height is not the problem - its upper body length. Long legs, short body = good; long body and short legs = problem
Best to sit in a car with a bar, with a helmet on, and have someone have a
good look. Then you will know if you have a problem, and the size of the problem.
One of the reasons the Sprint is uncomfortable is because there is little padding - good for a low bum heigth, which is what you want (can always put a cushion in for non-track use, which is what I do).
If you have a serious problem, you can always dispense with the rails and bolt to the floor. Legally dubious, and you will probably need a flat bottom steering wheel or similar, particularly if the seat is tilted back.