Best resource for understanding GC2 numbers

[mayassa]

No its a good point to know where you are hitting the ball on the head.

[p3eps]

My pro uses foot spray too to determine where on the club you hit the ball.
He said you get much truer numbers with foot spray than with one of the impact stickers - as the ball still sees the grooves on the club.

[SFR]

Only problem with a spray on the club is that your hitting screen might eventually get a bunch of ball marks on it from the residue. Duct tape will show impact well but like was said, any tape may alter the spin of the ball. Overall yardage did not seem to be effected.