Potting oncostele- too much seramis?

[reptilegrrl]

I need some n00b reassurance. I bought a very large oncostele Midnight Miracle 'Masai Red" at TJ's. It had 10 PBs and though it was deeply pot-bound, it had many many live or viable roots. (Although some of the roots were a little soft and will probably die in the future, in my experience it's better to leave them on while they are still alive and functioning, rather than cut them off when repotting.)

It was in a tall 4-inch pot, but when I pulled it out, it expanded an inch all around. Then when I cleaned, soaked, and untangled the roots, it was too big for my largest orchid pot, a 5.75" plastic pot. I needed to improvise, so I bought an acrylic serving bowl at Target and drilled drainage and ventilation holes in it. The bowl is a little bigger than ideal, about but I was in a bind and needed to get this thing in a pot, it has a lot of PBs and a lot of roots and it was very thirsty as a bare root plant. The roots do fill most of the bowl.

I read that this plant is a heavy drinker and likes a lot of moisture. So I potted it in a combination of seramis clay granules and red lava rock. Seramis because it stays wet for a long time. Lava rock because in my experience seramis can smother roots by creating a too-wet situation, and because these roots are not tiny, they are almost like a phal's roots. My hope is that the lava rock will create airy places inside the bowl- I know it also absorbs water, but not as much as the seramis, so my thought it that the seramis will pull water from the lava rock.

But I am second-guessing myself. I am super-worried about smothering this plant's roots and rotting them. The oldest PBs are a little shrunken since repotting. (I did find a lot of very dead roots on the oldest pbs and those were pulled off during repot. The oldest pb also popped off when I tugged a root so I have potted it up alone and am hoping it will propagate.) I posted a picture in the galleries. You can't really see much of the lava rock, because seramis fills every gap everywhere, but here's the general breakdown: the root volume takes up about half the total volume of the bowl, then the lava rock is about 1/4 the volume of the bowl, and then the seramis is the rest. But if you know seramis, you know that it fills spaces pretty tightly.

My environment: these are windowsill plants in my living room. They get northern light all day (bright shade), strong western light in the afternoon, and have an Ikea vaxer bulb directly over the Masai Red. The typical temp is 77-80' (central AC) and there is a ceiling fan on during most days, but I usually shut it off at night to give the orchids increased humidity (there is still air circulation, as we have AC and high ceilings.) The typical humidity is 48% but I mist all the orchids about 3x a day, which raises the humidity from the high 50s to the low 70s.

I really like this orchid, it is enormous and has big fat PBs and 3 spikes. I really don't want to mess it up by rotting its roots.

Thanks for any advice you can offer!