I wouldn't worry so much about length. Weight is more important, but even weight isn't as important as body structure.

And trying to compare BP growth rates is like comparing blades of grass. There are just way too many to compare, way too many variables and comparing to others will make you question whether yours is too skinny, too fat, too long, too short, etc...etc...etc...

Your snake looks to be in good health! Keep up the good work.