I agree with the others, put it in a larger pot. You could fill the center (or the botoom) of the pot with styrofoam packing peanuts (first make sure they don't dissolve in water) so that the potting mix won't stay wet for too long.

Haha!

I haven't gone that far yet, but I did recently move my huge Phal. White Dream 'V3', which had been severely leaning out of a 6 or 7" pot, into a 2-1/2 gallon painter's bucket. I got a silver/gray colored bucket from Home Depot and drilled numerous holes in the bottom and sides with a 1/2" spade bit. I also stuck little rubber furniture protector feet on the bottom, to raise it up for air circulation through the bottom holes. My current mix for this and other recently repotted large standard Phals is about 3 parts coconut husk chips and 1 part charcoal.

Obviously when using a container this large, I have to be very careful about watering. A bamboo skewer tells me it's still damp in the center from the last time I watered it a few weeks ago. I've just been generously misting the surface regularly and occasionally shooting a very little water from my misting bottle in through the side holes.