Don't shim the base to adjust Tram!!! When I first got my machine (2011) the tram was out .005+ over 8 inches. I saw a Youtube video showing how to shim the base, so I followed and ended up shimming the left front foot. It was better but I still couldn't get rid of the step between passes when fly cutting. Years later I was drilling a deep hole, .625dia x 4.5 deep. As it went deeper the load increased significantly (sound too). After drilling I found the hole to be .625-.626 at the bottom but .631-.632 at the top (measured with pin gages). This seemed to suggest that my spindle axis was not parallel to the z-axis even though it was perpendicular to the table (tram). So I bought a precision granite square (
10" x 6" x 1" Precision Granite Square) and went about mapping my machine (not going into the details of the process right now). I found that there was a significant twist in the Y-axis, when I removed the shims from the left front foot the twist went away, not perfect but pretty good. I was able to determine that the XY moved in a plane, with a little deviation, and the z-axis was perpendicular to both the X and Y within .0015 over 10". After that the Tram was out more than .005 in X and around .003 in Y. To correct the Y I shimmed the bolts holding the head to the Z carriage and to correct the X I removed one of taper pins, allowing it to rotate around the other pin. Now I can fly cut and have no (almost) noticeable step between passes.
This part is done with the superfly you can see the multiple passes but when I run a finger nail over it cannot feel a step.