I'm beginning to think it's 1 with the way I've been going lately, lol.
I think it depends on who the cons are. 3 good sticks that are actively working together can stretch my SA beyond it's breaking point. There have been times where I've kept track of 7 or 8 guys, but they were making it easy for me by staying on the same side, alt, etc.
On average, I'd say 4-5 is about right.