I'll go 20/16 7/6. Get one of your back guys out; maintain double coverage for your outer board; give more flexibility for filling your inner board (or running in someone from the 16 or 13 to 8 or 7).
The only plays I see are 20/15 and 20/16 7/6. My instinct tells me to spread 'em out, but I usually overdo that so I'm guessing it's correct to make the 16. It kinda feels like splitting hairs, though, unless I'm somehow missing something completely different.