Folkfreak, There are many digital scales on the market that feature non-magnetic weigh pans. You are quite correct that any scale with a ferrous weigh pan would give an inaccurate measure of VTF and might even result in damage to the cartridge suspension. However, as noted, this problem is easy to avoid.
cleeds, True, gravity is a constant for any particular location on earth, however, actual VTF will vary depending upon where the tonearm is located in its vertical arc. This happens when you play a warped LP, for example. Thus it is important to use a scale that allows VTF to be measured at least roughly in the same plane as that of the surface of a typical LP. There would be a tiny variation in VTF, depending upon thick or thin LPs, not enough to worry about in my opinion.
Chakster, Like Raul often says, Relax and enjoy the music. As many papers as there are on using a digital microscope to set SRA, it is nevertheless a skill that can only come from doing it regularly under the guidance of one of the very few experts in the field. I advise you to do it by ear. Azimuth is yet another can of worms.
