Phrag Mountain Maid flava Mix Suggestions?

[CPKidofAugusta]

I have a Phragmipedium Mountain Maid flava (besseae var. flava X hirtzii.) This happens to be the most expensive plant I've ever bought at $75 . But that's not quite as bad as it sounds, it's in a roughly 10 inch pot and had 10-12 growths with 3 flower spikes. After a period of neglect and excessive heat it declined a little bit, but i was diligent enough to keep its water tray filled, so now that I've been taking care of it well enough that it's ready to reclaim its former glory. With 3 fully formed growths yet to flower and five immature growths i'm in and about it. Only one problem. Not a single growth is growing towards the center of the pot. SO! Looks like I'll be turning it into 3 plants (but i'm happy to take other suggestions on how to divide it, please do look at the pics.) My only problem is i'm not sure which potting mix(es) I want to use. I was thinking about Carter and Holmes' besseae-type Phrag Mix (Three parts long fibered New Zealand or Chilean sphagnum moss (Soak for at least 24 hours, drain and squeeze out excess water), One part volcanic rock or ‘Dyna’ rock, rinsed (1/4" to ½"), One part #3 perlite (sponge rock), One part loose medium tree fern), but i don't want to plant all of them into one type of mix and find that with my conditions it's rot prone as a compost heap or so stagnant the roots might as well be trying to take oxygen out of concrete. So let's hear some other suggestions.

It currently grows in what looks like large fir bark, coco husk, charcoal, and perlite.