Peter, its interesting that you suggest a ledennii, was just admiring your golden ambion x ledenii,(thinking that i have to get a nice ledenii) do you think this hybrid would do well mounted, also might you have any ledenii or do you expect to get any.
In theory, you can mount just about all Phalaenopsis because they are epiphytes. But my target are ones that don't do well potted. I said these mottled foliage because they really don't like wet roots for longer than 3 days. If my collection is smaller, I would have these in bark mix and water them more frequently. But that's not practical in my setup.
Another group of Phalaenopsis I had trouble is small species. Two types - one (Phal appendiculata) that needs warm and moist all time. The other type (Phal wilsonii) that can tolerate longer period without water - yet still need fast and quick wet/dry cycle.
I've used small 1.7 inch pot for these. But my greenhouse is drier in the winter time. I cannot keep up watering these 1.7 inch pot. Larger pot will not work because it means roots stay wet longer.
You really need to know what works for you. One way to know is to experiment. This is why I am excited to try kool-logs. The evaporative cooling concept is not new. But I like that a water reservoir is there for me to fill up the logs when needed - and moss will not dry up and difficult to rewet as quickly. I will still mist the plants when I water. Also I'm trying to find a method that works for these challenging phals year round. Tight moss one-hole disposable clear pot works for most of my phals - except mentioned above. Hope this helps.