I decided to go with coconut husk chips, chopped sphagnum, and some charcoal bits. And I used round plastic pots with air slots.
I also migrated my Bulb. barbigerum and Bulb. medusae which I've had mounted since I bought them over a year ago. Despite all that time and some good growth neither of them were well adhered to their boards.
I'm thinking the new media will provide a lot more regular moisture. Wish me/them luck!