Alberto
I think it can affect...let me explain...
Higher is the pilot more it weighs...and weight affect results...
Exemple....
Pilot 1:
Height 1.80
Weight 78 kg
Pilot 2:
Height 1.70
Weight 68 kg
So, pilot 2 will be ever about 10kg lighter then pilot 1
As the difference between a high pilot and low pilot can also reach 20 kg you must prefer low pilot, so 20kg more is a lot....think like you have 20 liter more fuel...is about 20kg...and you can have 2 seconds difference in a lap for this
This is irrelevant (nor does it even matter) as a driver whose height is 1.8m can be trained down to 51kg and so can a driver whose height is 1.7m.