I only recently obtained my flask of sanderianum. I must say there were
several extremely large plants (6"ls) in addition to the usual size ones
and the tiny ones always present clinging to the base of the larger
seedlings. I have put it in the mix last year's flask compots loved. I
pot them all together as they come out of the flask in a mix of fine
bark, sponge rock and promix. It was an experiment last year, but the
seedlings really took off and have turned out very healthy, so now it is
my standard mix for compots. The compots of course go outside with the
rest of the plants for the temperate weather, and in the intemperate
part of the year here in the frozen arctic (Ohio) they are in the warm
growroom with the vandas, bulbos and phals. it gets down to probably 65F
at night (actually day; the room is on an inverted schedule) in there,
maybe 60F, and the humidity probably runs at 50-60% (higher for a couple
days after watering). Daytime (for the plants, nighttime for me) temps
run into the low 80's.

A recent comparison: my compot of insigne v.sanderianum 'Gladiator' x
self and the flask a friend has. Both from the same flasking; mine
developed contamination shortly after I got it so I took the then 1"
plants out and compotted them. They seem healthy and show no sign of the
mold I cleaned off them, but they are still 1" high, while the ones
still in flask have grown in the intervening 4-5months to 2.5" high. So
I have an object lesson there about deflasking too early (which in this
couldn't be avoided).