exerda

You could use a 1-liter sized bag to get a little extra volume. A liter is about 6% larger than a quart, and would be what a traveler from outside the US would have to use. (Likewise, with the "3-1-1" rule, it's actually 3.4 fl oz which should be allowed, to comply with the 100mL size pretty much the rest of the world has available.)

Some people have reported problems with the TSA going with a liter bag and 3.4 oz containers, but I've never had one (yet).

I have also had TSOs confused by the difference in weight and volume, having an obviously large shaving cream container that had recently been reprinted by the manufacturer to show volumentric rather than weight measurements (holding two identical cans side-by-side, one reads "3.4 oz," the older one "5.6 oz," the latter being by weight vs. by volume, as they weigh the same).