I think I range in that area. I have a BJ7 with BJ8 cam and HD-8 Carbs. I don't go more than 15* if I am aware of it. If I remember right, since there are no degree marks on the balancer, i think 12* is about 5/8ths of an inch and 15* is about 3/4ths of an inch. Someone might want to correct me if I'm wrong. But that is what I have been using. Sometimes I will advance it from there till I get some pinging, then back it down about 2*. But i have never put it more than 3/4th inch from TDC. I have zero experience with a petronics but I don't think it should make any difference in your base timing. Dave.