The Big Baron is hands down the most fun surfboard I've ever ridden. I've wanted one for a while and then magically found a used 6'0 in Oregon and it's completely changed my surfing. It paddles incredibly well, you can catch everything with it, and it goes on any wave type. The ease of turning on this twin fin feels like the board reads your mind and goes exactly where you want it to go.
I took a two board quiver to Costa Rica and only surfed the Big Baron. The 6'0 is now my everyday shortboard because it's so fun and versatile. But that being said, I know I'd have fun on just about any size. I'd imagine anything up to 6'8 would be very nimble and shredable, while something longer would add some stability. Looking forward to experimenting with some more fins, too.