i'd say 75-80%....because they don't take into factors like:
tempo
swinging or hitting (literally, the procedure you use will affect your fitting)
how good you "mash" the ball (ie smash factor)
release point
load
HOWEVER
If you get in with a GOOD FITTER, even on the phone, and be really honest with them they'll get 95% of the way.
PM me and i'll give you a good fitter to contact, don't want to post it here and step on anyone's toes.
__________________
I'm not a TGM or PGA certified Pro, but I did stay at a Holiday Inn Express last night