I just got off a two boat, three person. 24-day-to-South-Cove trip. People are good down there, and will help you if you need it. We offered to help folks who had flipped, and I'm aware of a commercial motor trip that helped a flipped private raft during that time as well.
However, there is a reduced margin of safety with a one-boat, two person trip, and only you can gauge if you're prepared for that. We saw rattlenakes close up and personal, you can slip and fall and break something, and other things beside flips can stir things up. For sure, as Caspian says, keep your rescue gear where you can get it if you flip, know how to rig a Z-drag, and don't do anything too wild and crazy.
On trip numbers, if you can pick up some additional good, experienced folks at gcpba.org, that would be great. But don't be persuaded that you should take more folks than you actually want to just because the permit max is 8 or 16. It's your trip and you have every right to make it what you want, not what other people think it ought to be.