Very interesting so far! A true labor of love. How much money invested so far? And then add to that a figure of your hours put in and attach a monetary value to that as well. I understand that you must enjoy the challenge, but when you add it all up, if you had just went out and bought a small used 3 axis knee style CNC machine, you would be making parts to sell right now. I have many projects laying around my house (and in the driveway) and to the regret of my wife, I think I will get them all done in a reasonable amount of time. It has not been so for years. But keep us posted. Have you looked at some of the designs already out there? You mentioned the aluminum plate. BPT (on the original Z drive EZTRAK design) used a 5/8 inch steel plate sandwiched between the head and the knuckel as a mounting surface for the drive components. That required longer "T" bolts to hold it all together. The latest design was made by ELROD and mounted to the front of the head. Very similar to an old BANDIT design I saw many years ago.
George W.