How to repot this large Cattleya

[NYCorchidman]

Any backbulbs with viable dormant eyes are capable of making new growths.
Dividing may set the plant back, and sprouting of dormant eye(s) may take a long time depending on the plant.

A trick I read about is that you make a half way incision(s) on the rhizome, thus inducing the plant to wake up dormant eyes on older leads.
Once you see dormant eyes on older leads start growing, you can safely make divisions.

[dounoharm]

every couple years I had to repot or divide some huge cats I kept...in 10" pots....no choice there but chop something off, lol....I would take them out of the pot, usually plastic ones because I hated busting the clay ones....they normally have enormous root balls....so, I would go horizontally and chop off half the root ball, then put my fingers thru the remaining roots to pull out loose roots, cut any dead spots out, find a weak spot in the rhizome to cut, and cut for a division. I repot with large firm bark chunks, charcoal, and perlite....by taking out some of the old roots, it gives room for the roots to regrow into the new media...in a year or two, it happens all over again....after repotting, I don't water for well over a week, to give the cut root ends and such to dry out and heal....best time to pot a cat is when you see new root development start...good luck!

[Orquiadicto]

Some time ago (july to be more specific) I repotted all my cattleyas into clay pots with leca, volcanic rock, perlite and some sphagnum. I planted them with the back bulbs against the back wall of the pots to give the new growths in front space to grow. Since then, they have been putting out new roots and new growths like crazy and even the old bulbs are putting out new roots and even new growths (that eventually will grow out of the pot since the back bulbs are against the rim of the pot). When they outgrow the pot, I'll just have to put the old pot into a bigger one and fill the pace with this same medium. I'm not going to divide any of them. I hope for big specimens.

[dounoharm]

i think you will find that the specimen to be will grow faster and better with medium in the pot rather than just pot after pot inside each other....roots need medium for stability and some nutrients...as the plants get too big for the pot, just smash the clay pot, and trim a bit and put in a larger pot with more media....good luck!