guess I don't quite understand, are you moving the rowing seat back to the dry box?
Here's how I run my 14 vanguard on multi-day trips:
front bay is drop bag and nrs table. I put lots of misc stuff in the drop bag, firepan, rescue stuff, chairs, squirt guns, cases of pop/beer, collapsable buckets, handwash, pump. I can fit the groover in there if I rearrange.
Yeti goes behind that, rolled pacos on either side of the cooler; then rowers bay, I don't have captains boxes but they'd be nice. I have a foot bar behind the cooler with the umbrella mount in the middle.
I sit on the dry box and use the gear pile to lean against.
that dry box is either extra storage for misc gear, dutch ovens, food etc. on trips with lots of boats. or on trips with fewer boats it's the kitchen box. Two 7 gallon water cubes fit on either side of the dry box on top of the tubes.
In the back I can stack a layer of 5 buckets, gamma sealed for food. At least three of those buckets will be stacked into empty buckets for handwashing or dishes. On top of that layer goes the dry bags, then a king sling over the pile.
The problem on the vanguard is the thickness of the floor cuts into the cargo volume so you have to pack well. it's not a very deep boat. I've changed a lot of cross bars around over time