Beaming in 12/16

I had the misfortune to have to enter a classical movement in 12/16 (https://musescore.com/bsg/christe-eleison-bwv-242 ). I had to teach it what that meant, of course. I told it how I wanted the sixteenths, and it got that right. But it wanted me to tell it how I wanted eighths, and eighths are not a meaningful subdivision in 12/16. After sixteenths, the next bigger unit is dotted eighths.

I got little help from MS in 12/16; except when there were uninterrupted runs of 16ths, it was tough sledding. I don't know what the generalizable right design should be.