And other reasons I adore the English language. I am going to try to catch up on the progress the machine has made, because a lot has happened lately. The results are that we have a darn good working machine (as you can see in the previous video) and it's only getting better as we learn.
First, once we put the spindle on some new flaws became apparent. We were getting a lot of chatter, the source of which we determined by means of high speed film (thank you modern DSLRs). The rails on Z were flexing, the whole frame was flexing, and all of that was leading to problems. This wasn't apparent with the router tool because it was taking off so little at a time (and creating a ton of heat, and taking forever).
So I replaced the Z rails with the next size up and triangulated the frame, adding a truss to the back of one mounting beaml: