Just one comment about the much misunderstood underhung group of tonearms. There are only a very few of them that I know about: RS Labs RS-A1, Viv Float, and the Yamaha. Can anyone name others? These are all straight tonearms with no headshell offset, and they all underhang the spindle. As such, only one single null point is possible on the surface of the LP. The best way to set them up is to arrange to place the null point (cantilever parallel to grooves) somewhere at or near the middle of the distance from outermost groove to innermost groove. These tonearms exhibit a great deal of tracking angle error (TAE) at the outermost grooves, more than one would ever calculate for a conventional overhung pivoted tonearm. TAE will be inversely proportional to the pivot to stylus distance. TAE then diminishes linearly as the stylus tip approaches the single null point. Also the TAE results in a skating force that is similar to conventional skating force, with a net vector directed toward the spindle. That skating force also diminishes linearly with distance from the single null point. With this type of tonearm, at the single null point, skating force is also zero for that one instant. This is different from conventional tonearms, because in that case skating force is never zero; even at the null points, there is skating force due to headshell offset. Once the underhung tonearm has passed through its single null point, TAE begins to increase again in a linear fashion, as the stylus approaches the innermost groove. BUT the vector direction of the skating force that goes with it is in the opposite direction, pulling stylus tip outward. That is why you won’t find an anti-skate device on an underhung tonearm; it would be very difficult to imagine an anti-skate mechanism that would "know" when to change direction.
Like I said, these tonearms do exhibit a lot of TAE, but TAE does not wax and wane as it does with conventional pivoted tonearms, and there is a period around the null point where the skating force and TAE are very low to nil. The understanding of these tonearms is complicated by some of the foolish and patently false claims made by their makers. The RS Labs instructions say that there is no skating force with their tonearm, which is wrong, for one example. But on the other hand, they sound more free of artifacts that one associates with TAE and skating force than all but some of the best linear trackers, without the complexity associated with those types. I wish there were more underhung tonearms from which to choose. I occasionally use the RS Labs, but I shy away from it because of its other oddities and potential danger to cartridges. But the RS Labs occasionally can sound like a master tape in its very stable imaging and low audible distortion. This observation leads me to question the wisdom of offsetting the headshell in order to achieve two null points on the surface of the LP. This results in a skating force due to the offset angle and in TAE that varies up and down in magnitude across the surface of the LP. Perhaps the variations in TAE effected by headshell offset angle and overhang make any resulting distortions more audible than they would be if the changes were more linear, as with an underhung tonearm. After all, Baerwald and Lofgren published their math in the late 1930s or early 1940s. If they even listened to music, they were doing so with wide-groove mono shellacs playing at 78 rpm (I am guessing). They couldn't know what the future of the art form would be. Why do we have to cling to their old ideas?
