The method I use for cramming maximum volume of crap into my 14', and still have passenger space, is to rig a table over the bow of my raft, and fold a paco in half over the table. I have been using this lifetime brand table which my dad got from sam's club dirt cheap, for the last ten years. I rig short straps through the corners, which I attach to my corner D-rings, and front cross bar of my 3 bay frame. Also add a loop strap over the middle of the table from cross bar to front inside D-ring. This makes a good spot for my water jugs, and some rockets underneath. I leave the corner straps on my table so I can strap my dish rack to it at camp. Stainless loops tied on the ends of the table to help with rigging, and I can use them to strap the table down to my kitchen box and a water jug in camp so it doesn't blow away.
I ran a 12' hyside a couple times guiding, they gave me 7 passengers, and I looked at them like they were nuts, but what a fun ride! I found I could just submarine through just about anything, as long as I hit it straight!!