I think your string will be fine, and it may stretch a bit also. Is it fast flight or B-50?
Depending on how tightly twisted the string is you can adjust it by twisting it. "Normally" Clockwise to lenghten, and counter clockwise to shorten, but keep an eye on the string while doing this see what it's doing. I know some left handed guys who make strings and they twist them in the opposite direction of a righty.