01-24-09: TvadI've had my SL1210 M5G for nearly two years now. I started with the plastic jig and an M97xE and go OK results, but I've since moved to the Vinyl Engine protractor referenced by Tvad and I've been *really* happy with the results, both with a Denon DL-160 and my current cart, an Audio Technica AT150MLX (a superb match w/the Technics, btw).
The Technics white plastic jig does is not accurate. It does not allow for cantilever alignment, nor is the overhang optimal when one compares the results to that of the MintLP or this Technics arm protractor downloadable from The Vinyl Engine (scroll down the page). Be sure to download the instructions as well.
I also agree that VTA is best adjusted by starting with the tonearm on a record eyeballed to horizontal, and then adjust VTA on the fly until you dial in your optimum sound. Use a variety of music to get a good average setting. What gives you the most vivid cymbal crashes may not be the same height that gives most satisfying female vocals.