I was previously a 5 boxer, but then expanded to 7 boxing to level 3 new teams to take advantage of previously single-boxed mid60s I had lying around.

You're definitely better off quad boxing the two pairs of two together. It's what I've been doing and my first RAF team, 4 mages, has hit 48 this morning (Thursday morning). I made them on Friday night the previous week and at 48 they have just 1 day, 2 hours /played.