Late here, but it's hard to underfeed a BP if feeding at least every 2 weeks and being given appropriate sized meals.
As bogertophis said, he's still growing, so I wouldn't worry too much. If you go to a less frequent schedule - like every 10-14 days, it won't hurt him, he will only grow slower.
I disagree with the feeding chart on duration once BP's are adults though. Every week is too much IMO. I have also found that smaller meals are better for adult BP's than larger meals. Shayna, my 9 year old female BP, eats like clockwork on small rats every 2 weeks. She's over 1,800G. She does fast in the winter, but rarely ever skips a meal otherwise. On medium rats, she would skip meals often when offered every two weeks. She puts back her weight (that she loses during winter fast) quicker and seems more active and healthy on the small rats as well.
I do not think one size fits all, but it's difficult for snakes to lose fat once it's put on.
He's looking good BTW.
EDIT: Small rats to me are 60-90G. 50G is a weaned rat, at least from my suppliers. I buy from perfect prey and big cheese mostly.