The boats we ran all had suspended wooden floors, with about a 4" gap between the rubber and the wood. When the floors weren't leaking that is.
On the wooden floor we stacked coolers, food boxes, kitchen boxes, groovers, bags, barrels, ammo cans, and any other damn thing we could. We lashed it all down with rope, running from the frame and randomly through the stuff we stacked onto the floor. Lots and lots of entrapment possibilities. The boats weighed enough that flipping was not a real concern on most of the rivers we ran, but even on Cat or Grand Canyon, outfitting was basically the same.
Never felt there was a real chance of some kind of entrapment. Never had an issue. I know that during those years one guide was caught in his load in the Grand Canyon and died, and another had a serious scare on Ladore.
You have to do what makes you safe, but for what it's worth, in my opinion, this is one of those topics that gets over thought and over engineered.