A stack of 12 checkers sounds unwieldy and precariously fragile. I would keep all but a few of the Queen’s checkers in a reserve area near the board.

Yes, good point, many stacking games suffer from the excess of manual dexterity needed to play them well.
Fortunalely Ed van Zon has agreed to make an applet before the end of the month, so that the game can be played without any distracting physical behaviour at mindsports.nl :)