Well, I guess I will answer my own question for those who run into similar. You can buy the M54 filter drawer, unbolt the male M54 portion and it is a perfect match for the M42 portion of the existing Nikon and Canon filter drawers. Kind of sucks that the only solution is $160 but at least you get an extra filter tray. ZWO already has this part; please sell it separately. This affects ASI6200 and all Duo users as well.