Update: the tree is still doing well. The foliage has thickened up quite a bit but I have a big drainage problem. Water does not percolate through the roots well at all and due to the size or the pot the tree tips over very readily. Keeping it from tipping over is easy enough, but the percolation issue is a concern considering how hot it gets here in the summer. I am worried the tree won’t get adequate water when it is hot without a repot. I bought a pot that might fix both of these issues, but I’m worried it may be too radical of a shift in design and wondered what others might think. If anyone has other pot suggestions, or other suggestions in general let me know (especially if you have a pot or vendor to recommend). I’m not really itching to mess with it, I just want to make sure I have free drainage and more room to hold substrate so I can keep it adequately hydrated in summer. Currently it hasn’t been a big issue but I need to be prepared for temps well over 100 if we don’t have another mild summer.
So, I ended up selling mine before the end of last year simply because I feel like I sorta got what I wanted out of it (up close and personal time with a tree of this caliber to try to figure out how it was made). That said, IF I had kept it, I likely would have kept it in the pot as-is (or one of a similar size).
I may have repotted this year just to free up some space, but my understanding is that the short needles would in part be due to the watering technique and pot size, which Suthin controlled up until it was sold. Too much space, and the tree will grow too vigorously and knock it out of whack - at least, that's my understanding. My plan had been to attempt to continue on the path Suthin had started.
As always, I'm open to being corrected, but that was my thought process. I just kept looking at it, thinking about how people say "if you can wire one of these you can wire anything", and realized I couldn't wire anything just yet. I didn't want to start with this. So, on it went, hopefully to someone better suited for it to keep it looking good for the long haul.
In terms of the watering issue, you might try placing it - in its current pot - on a tray with old bonsai soil. You could even fill that little pot you got and set the current pot on that soil. That should help it maintain moisture throughout the day, though I imagine in Texas you're going to need to keep a close eye on it.
Long story short, though, is that my assumption is that if Suthin did it the way he did it, he did it for a reason, and my goal if I had kept it was to continue with his strategy.