Oh good, good luck with your sanderianum!!
My masdevallia is actually in straight up moss in a clay pot already, so hopefully it's doing alright then! It's definitely rather cold in this house to begin with, so I have a feeling it's happier about the default climate in here than all of my others are. (The others get heat mat time.
)
I have my phals in bark in clear pots--for some reason, moss and phals just don't mix well in my house--they always rot out on me. They're very happy in bark here though. Do you tend to have better success with net or clear pots?