Start with about a 10% reduction for the back off set and adjust from there. Weighted Chins will almost always going to be a better option than Lat Pulls for strength training. There are some advantages to doing Lat Pulls over Chins in certain instances but those instances probably don't apply to a guy just coming off LP. So keep chinning. Also keep in mind when you read my articles online that most programming examples......are examples, unless I'm citing some very specific routine or protocol. Don't read them as exact prescriptions FOR YOU.