I got Penelope at the beginning of August and she was a very small 10-11 month old at only around 130g empty. Since then I have been feeding her f/t weaned rats every 5 days and she's now nearly 500g. She doesn't appear overweight, she has a very firm muscle feel to her, and she's just all around much larger than she was.

She definitely acts very hungry at the 5 day mark now, and I'm thinking the ~40g weaned rats might be a bit too small for her now, and I figure it might be a good time to start on something bigger every 7 days instead. I have heard that the 10-15% rule is only for hatchling and juveniles though, but would she still qualify for that given the fact that she is still growing fairly rapidly even though she is just over a year old, or should I just go by width at this point? If so will I continue to do that from now on, or is there a maximum size rat even if the BP is quite thick?

I guess I'm rambling a lot when my question should just be:
What size rat is suitable for a 500g BP every 7 days (I'm not sure whether to order small or medium rats), and what is the maximum size rat that you would feed to a full grown female on a 7-10 day basis? I know there is a range of right answers and it's also based somewhat on opinion, so your opinion is fine, assuming you have experience with the size of BP in question.