Passengers in the front = water shields so the captain stays dry
Pull those thwarts out, you don't need it in a 18 foot rig! You got way more than enough flotation there. Drop some dry boxes/drop bags in those sections and stick a table on top to cover it. Then your passengers can sit on top of the first platform.
Most people run their rig boats in 4 sections.
Bow = Passengers
1st bay = drop bag or dry box covered with a river table
2nd bay = cooler
3rd bay = captain area, captain boxes, water jugs
4th bay = dry box/drop bag with possibility for a captain seat
Stern = gear pile
Dan, I live about 20 minutes from you, you are welcome to stop by and check out my boat.