when do I pot or mount seedlings?

[Yourneedfulthings]

I have 30 or so Bulbophylum echinolablium seedlings 3 months out of flask doing great in moss compot, plants are about 1" max.
I would like to eventually mount them in tree fern, many in one big slab. First question: is that a good idea? and if so at what age/ size and how far apart do I place them?

My greenhouse has a humidifier set at 70%, during hot days it drops to about 40%. Summers are hot.

Is the flower stink be tolerable with some many of these plants? I know it is years before that but I'm always thinking ahead.