I think we said in the other thread that the smallest dimension was 8" depth. Both length and width allowances will be a bit longer in this case because the smallest maximum I've seen was still 45 l.i..
Thus if you go with a bag that is not more than 20" long, 14" wide and 8" deep it will fit all regulations and all sizers. BUT it won't be the maximum 45 l.i. anymore. You lose about 540 cubic inches compared to the US domestic standard of 22x14x9. The bags said to be of that size are in reality often bigger, though. 540 ci is a space 10x10x5.4 inches. So that's some good packing space there. I'd say the volume of two khaki pants or so.
Still if you know how to pack, not a problem.
Till