Yea, I went so far as to call the company and talk it over with them and a couple locals that had been on the river before going with that smaller raft. I was under the weight limit by a decent margin and had the space, but just couldn't maneuver and cut back quickly like the river dictated. It was flowing higher than normal which didn't help my cause.
A larger raft may have helped but there were certain parts of that river that I could barely squeeze the small raft through between the bank and fallen trees. A larger raft would have been more stable so maybe it would not have not flipped, but it would definitely have been pinned and hit a bunch of debris, not to mention bottoming out frequently on the shallow stretches. That was unavoidable regardless of raft size. It just wasn't an ideal setting for a raft under a heavy load.
As far as bow hunting, it definitely would be doable and I thought about bringing mine before the amount of gear started adding up. Some animals were skittish but many weren't. The wind seemed to be a bigger factor than sight even on if the bison was concerned.