Several people have asked if it would be possible to make a self-bailing or inflatable floor using the double-layer floor option, and I have finished retrofitting my multi-colored packraft with an inflatable floor in just this way.
The inflatable floor is a great success! It adds padding between you and any rocks or sticks you might paddle over, which protects you from injury and decreases the abrasive force exerted on the fabric. It also insulates your legs from cold water.
Instead of heat sealing the entire second floor layer to the bottom layer, I added baffles between the layers to hold the layers 4-5 cm apart (similar to my seat design or a camping mattress). I then sealed the perimeter of the upper floor layer to the bottom floor layer after adding a small inflation valve near the edge of the floor (the volume is small enough that it can be inflated by mouth).
If you don’t want to go to the trouble of adding baffles between the floor layers, you could simply heat-seal the layers together in parallel lines, but it’s not difficult to add the baffles, and it’s not much material, so the added weight is only a few grams.
It would be very simple to make this floor self-bailing by heat-sealing a few patches of the upper floor layer to the lower floor layer near the rear of the cockpit (i.e. the lowest point when afloat) and cutting holes in the center of the sealed patches to allow water to drain out.
I will be adding a spray deck to this packraft, so I won’t make it self-bailing, but for those of you who enjoy whitewater paddling in warm climates, a self-bailing floor would be a good option.
With an inflatable floor, the packraft can also be used as a camping mattress!