Hi Pib85 and welcome to the Plumbing pageat at AskMeHelpDesk.com. You piggybacked on an a 4 year old dead thread. In the future, before you post, look in the upper left hand corner for the date. I agree with Mark,
We rough in at 12" off the string and the drywall is 5/8ths" not 1/2".
Cheers, Tom