I assume SS, and good running motor.
This is based on R6 and GSXR750s start with stock gearing if wind is down back straight or calm. If calm to headwind down back straight start at one tooth bigger on rear. After a round of practice I would drop one rear tooth. This is based on championship winning Am times and top 10 Expet times. For FUSA or winning Expert times probably 1/4-1/2 tooth more off back.
I know you can't take 1/2 tooth off so look at a gearing chart. 8)