Ok... so here's the result of my 16X wobble-issue:
I tried reseating the original (CYT) tire on the rim myself per @Mark Lee's suggestion -- but no luck. So I sent the 16X back to @Jason McNeil... he said the CYT tire that came on the wheel was defective and he replaced it with a CX tire (which was a bit of a surprise). So the wheel came back... and now... it's definitely better!
Here are my observations and thoughts:
The CX tire definitely has more of a "gyro effect" -- meaning the wheel is VERY easy to maneuver when going slow... but as soon as it gets up over about 10-12 MPH, it really stands-upright and requires a significant amount more lean to make it turn. This isn't necessarily a bad thing... but it's quite pronounced and required me to take it easy before I got used to it (nearly crashed it the first time I got back on, as I wasn't used to the amount of effort to turn it at speed)! Now that I'm used to it though, I actually like the effect quite a bit! It feels MUCH more solid and stable at speed and I was able to go from my previous wobbly max-speed of 18-20MPH now to the alarm I set at 25MPH without feeling like it wants to buck me off!
One downside, however, is now I'm noticing wobble on acceleration and braking (whereas previously, with the defective CYT tire, it would wobble just trying to go straight and steady down the road). This was much more pronounced when I first got it back... and now that I've ridden about 50 miles with the new CX tire (and also lowered pressure down to 25PSI) it seems to have calmed-down now quite a bit. Maybe I'm just accelerating and braking faster? I'm hoping this current wobble is mostly due to a skills deficit and will continue to improve... but I suppose between the CYT wobbling all the time vs. the CX only wobbling on acceleration or braking, I definitely prefer the CX because of the stability at-speed. I can now ride seated without wobble (a BIG improvement) and I do feel that I have some control over the wobble now as it only happens if I accelerate or brake too quickly, assuming of course I don't have to brake in an emergency situation, which I suppose would be dangerous... but as I said, it seems to be improving with my own skill. I can also run at 25PSI now, whereas with the CYT tire I couldn't go over 22PSI, which then made more noise and had more "bounce" just going down the road and also contributed to the unstable feeling.
Now... overall, I LOVE this 16X and feel like I made exactly the right wheel choice for my use of mixed roads & trails here in Northern Colorado, both standing and seated. It's a huge upgrade over my V10F -- it's MUCH more capable: I can go up some pretty serious hills without stalling, I can finally pendulum forward and backward, ride backwards as long as I dare, go down stairs without fear, and I even went UP a curb yesterday now that I have the Roll.nz bodyguard! Woo!
The biggest downside I have now is that I've outgrown the V10F. What to do with it? I'm thinking to list it here for sale... It only has 250 miles on it, a few scrapes, but it totally worked for the purpose of bringing me into the hobby before I was ready for the 16X. On the other hand, I would still like to have two wheels -- but what should the 2nd wheel be? Nikola? (maybe too close to the 16X?) Mten3? (maybe too small and twitchy?) Monster? Other? Would love to hear others' thoughts!