I kept Helene on a drying mud mooring. Generally all okay. I originally left the keels right up. I twice had issues with the keels not dropping immediately when being lowered after being left, but both times the mud pushed into the boxes let go after a few seconds. The first time I hadn’t paused after a few turns and there was a bit of a clonk!
But loosening the clamps and leaving the keels dropped an inch or two sorted it and didn’t have any more problems. The slight working of the keels on settling and floating off helps the mud stay loose. Best loose off the keel bolts though to minimise unnecessary wear.
And Helene is still moored on a drying mooring with Jim, although not quite a ‘mud berth’..
So, there shouldn’t be any issues. If the mud is really soft and time between going sailing / dropping them is long, leaving them slightly down is a good idea.
It’s worth noting that over the years many Atalantas have had drying mud moorings.