Every time we hit the river we make small modifications to how we rig. I run a 4 bay frame on a 15' raft. The front bay is slightly oversized (30"deep) so I can fit up to 6 rocket boxes in the drop bag with but I usually carry 3 rocket boxes and 4 produce buckets. Over that goes my table, gear bags, and pad. This makes a sweet lounging bench for the wife and kids. I sit on the primary cooler (128 qt) in the third bay. I have a secondary cooler (168qt) in the fourth bay that has been both a vegy cooler or a semi-dry box. I usualy strap a gear bag on top of this cooler so I have a backrest to lay back on. In the stern I have a homemade "everything" bag that is big enough for everything else. It is roughly 4'tall, and 5' across, and I usually put 2 straps over the whole things on rig-to-flip days.
The pics are from last years GC trip and show it fully rigged, and unloaded at camp. I am a big believer on unloading as little as possible
The Vittle Vault (on the starboard side) is used as my dry storage for on river snacks, hats, rain gear, and miscellaneous stuff. Also on the starboard side, next to the rowers seat, is a small 19qt cooler that I use as a small day drybox. It holds the maps, books, lotions, camera and other small stuff. On the port side are the handwash and settling buckets.
So far this is the best I have come up with, but I am always keeping my eyes open for a better way of doing it. The only mistake you can make is not trying new things. Good luck and enjoy. This is what makes the cold winter months go by.