My son is wearing a 6 and I am wearing a 13 cu-ft. You need to go through the calculations and assumptions for yourself, but a 6 cu-ft is probably fine for 80 feet, I use a 13 for past 100 ft myself. I made this video because i get tired of people saying a 13 cu-ft is way too small.
[video=youtube_share;r-L9extLDZQ]http://youtu.be/r-L9extLDZQ[/video]
I have a 13 as well. I've never surfaced with, but I've done the math with gas use and my primary. Most of my diving is <100ft. I can surface and do a safety stop. And if I had blow off the stop, I would. I like the weight and buoyancy characteristics better than the 19. But that's me.
I don't solo often, but if I do in the ocean, I'll take it. I do solo without it at bhb. But that's not really an issue.