I'm only 5ft 7 and was running it fine. I used the std seat on the road and this on track and never noticed a difference. Both are lower than my R1m was on the std seat.
The M seat is very slightly higher but as its firmer you notice the hight difference. The M is wider too so overall it feels higher than the standard seat with feet on the floor.
I?m guessing the standard height M seat would still be an improvement over the std non M seat as it?s either shaped differently towards the top or has better material for track?