Thanks... Believe it or not, but the only part that's not 'off the shelf' is the guard tube on it. I had the groove machined in it. The next time I do that, I'll have the tube longer when I give it to the shop, so that I can cut it closer at the top and bottom. Under the nuts, where the tube goes in, is silicone o-rings to hold the tube. I also have one on either end of the welded tube setup, so that the glass isn't directly against the metal inside the fittings. Under the guard tube, over the glass tube, is an o-ring at the top and bottom. That prevents the metal guard from hitting the glass tube.
I do find that when I have the shield metal under the keggle (to block heat from getting directly to the ball valve) positioned so that it's also under the sight tube, the level is rock solid/stable as I boil. Otherwise, the liquid in the tube gets to a boil, and it throws the readings far off (basically recirculates).
I can also clean it in place, by simply running the cleaning solution/water through it from the top fitting.