I have heard it suggested that small drybags could be inflated and used as a pillow. Have you heard any accounts of this?
I guess I continue to mull over positive-pressure applications for roll top closures because I can't see why they should necessarily be leaky. The standard buckled canoe closure crumples and creases the material, and I can see how these folds could be leaky. But, as an alternative, I tried rolling the material tightly around a tube, and it still seems to leak under pressure.
If a way could be found to make a truly airtight roll top, a single bag could then serve as a water bag, a drybag/stuffsack, an inflatable pillow, and a pump for an inflatable sleeping pad.