It would be better to 4 box than to 5 box right now
It's only better to four-box than to five-box if you want to four-box rather than five-box There's no reason at all why you can't five box and get triple XP on all five characters.

But that wasn't the question. The original poster said "minus R-A-F", so RaF isn't an issue here.

I'm disinclined to spend my time answering questions that have been answered dozens of times before, but I did want to quosh any idea that you can't use recruit-a-friend with five characters.