Back to underwear...
Well, when I started getting cases for my decks that were custom, the need for deck underwear seemed moot. But now that my custom cases are no longer available, and I am exploring other options, back to the option of underwear to keep cards in place! When you have a deck that is in a bag or case that it slooshes in, getting a pair of women's DRESS (think silky slinky) socks or knee highs and sliding the deck into the sock makes for a good fit in any case or bag. If the socks are too long, I just cut them off and/or knot them before plopping them into a case.