The shortest feed schedule I do is 5 days but normally its 6-7 days. So id suggest goimg to a 5 day schedule if you want to bulk him up faster and still hold. Its a marathon not a sprint.

As far as moving to 15 its really peeaonal preference. I prefer to put babies in 15 qt with multiple hides and stuff in there to make them feel secure. But some people keep them in 6qts intil 300+ grams. Ive never hAd a problem woth the 15s. my smalles is 120 grams in a 15 right now.

Hope this helps.