I don't have any personal experience with Natural Mystic but Pine Island Nursery says it's a magenta-colored variety from Thailand and that it too is self-fertile (the only other one they carry besides QOSF/AB). A grower in Mexico has confirmed this.
What I think you might want to do is to use a PVC cross (or I guess a cross and then above that a T) at the top of a center pipe and then go out about 2' each way at the top with additional pipes. At the end of those, you could use elbows without gluing them in and then have pipes going down to the ground to keep your plant balanced.
I've planted most of mine in a half of a 30 gallon plastic barrel with two plants in each "pot". It's about 20" wide so it's pretty stable, but I'll brace it if it becomes very heavy.
Yeah, I don't think you can grow any pitaya outdoors if you get down into the very low 20s or lower. But I think some can probably take even lower than 26F if they have some overhead protection from hard frosts. But in January 2007 we had several days where we stayed below 30F (with one night getting down to almost 20F) and I don't think any of them would survive that without some supplemental heat.
I don't know much more about George other than the fruits I've tasted of it were not very sweet.
I've got way more varieties than I should have but I guess that's because I keep chasing after ones that I've heard great things about from hobbyists around the country and even Spain, etc.
I'm considering building a small greenhouse to get more serious about these things as my plants will be pretty hard to move by the end of this year. My wife is very tolerant of my hobbies, thank God!
There's a fairly new bi-colored magenta/white variety being grown in Vietnam and I'd like to find some way to get that too. I do have an import permit so I just need to find a way to get it here, though I don't know anything about the tas