I was in Dollar Tree the other day and saw a piece of foam board, approximately 3' x 2', for sale for......$1.
Bought it, took it home, cut out a piece about 12 1/2 inches x 12 1/2 inches and it works great as a folding board for the Aeronaut--with or without the large packing cube. (This should work for both versions of the Aeronaut.)
At first I thought I'd need a pair of box cutters to cut the foam board but a plain pair of scissors worked great.
I don't like to roll my button down shirts so this works well to make sure they fit properly in the bag.
If you use a different bag, you could cut the foam board to match that bag. Just make sure it's a little smaller than the packing area.