What is more accurate: magnetic anti-skating, or barrel weight attached a fishline?

Tangency (null points) is not enough to eliminate skating force. Lew says it quite well, but maybe it needs to be said a different way as well.

Skating force is the vector sum of the forces of the record "dragging the stylus in a generally forward direction". Forces sum and cancel each other.

The amount of drag and its direction is a function of groove friction and geometry. The friction part is what makes it tricky, because this in turn, is a function of record velocity (changes across the record), the dynamics of the musical passage (varying resistance to larger "wiggles" in the groove), the condition of the vinyl, the shape and polish of the stylus, and ... I'm probably forgetting something, but you get the picture.

Here's a visualization that might help (and spare you the vector math): 

• Hold your left arm out in front of you (horizontally) with your palm facing toward the right.
• Bend your wrist so your fingers point further to the right, so it resembles the headshell/cartridge offset.
• Have someone tug on your fingertip in a direction parallel to your bent hand.

This is our null point case. Your hand will move to the right (skating force).

So, even at the null point, there's some skating force.

As Raul and others have correctly stated, there is no single correct anti-skate setting for your rig because of the frictional factors I mentioned in the third paragraph. 

Cheers,Thom @ Galibier Design

I have always imagined there are two different forces involved.  One, is as you describe, due to the offset of the headshell.  The second due to the "North - South" position of the headshell.

Imagine if you will a circle bisected horizontally through the center.  The line running from the left to the center, or at least towards the center is the line a Tangential Arm would track.  Assume a nine inch arm.  Now imagine a six inch arm.  It will be forced to the left because at that position the clockwise rotation is pushing to the left.  Likewise imagine a 12 inch arm.  This time it will be pushed to the right (towards the center).  

So to my way of thinking: before the first null point and after the second null point there will be some force away from the center towards the left edge.  Between the null points there will be force towards the center.

Then summing these two forces: Between the null points there will be a relatively strong center pull.  Outside the null points there will be a weak pull, though in what direction and how weak I could not say.

Indeed overhang/underhang, in conjunction with the frictional forces imparted by the record groove on the stylus are the key actors in this play.

I haven’t thought about the underhang case you brought up in a while (for the pivoting, 6" arm in your example), but Indeed it would appear that its natural state is to skate outward rather than inward- this, even if one had a reverse offset angle on the the headshell.

The only underhung arms,I’ve encountered were in a used record store, years ago - some DJ rigs set up for auditioniong records.

Cheers,
Thom @ Galibier Design

I really don't think the method is of the greater importance but using a record such as the Shure set  up disc or one's that have been coming out lately.I had my anti-skate set up  based on all other factors but when I used a new set up record it showed how off I was.
Using the record you want (Shure ,etc). When you have everything else set up  you watch as the tThen you know its more or less how muconearm stays in the middle.It does not drift left or right is simply stay more or less in the middle.

Pureharmony21@gmail.com

And finally, if this message still leaves you feeling anxious, there's always the linear tracking tonearm option.  No matter how you slice it, LPs rule.

That's true and genius.
THANKS!

Dear @ct0517 :   """  7,630 posts Raul and not one that I have seen that offers to share information or shows any ability to set up a LT tonearm.  """

I can't understand why you " insist " with the LT subject, no one but a few use that kind of tonearm design. Tonearm designers deciding go for the pivoted ones. Kuzma owners of Kuzma LT tonearm change it for the pivoted 4P.
Analog experts as M.Lavigne or A.Porter changes theirs Rockport Sirius and Walker both with LT tonearms and today use pivoted tonearms with out the need to turn around again for LT designs.

With all my respect to you in your system you just can't be aware of the LT limitations against pivot tonearm designs because for that first you have to own first rate top pivot tonearms not those non-damped very old designs that are not a good example of what a pivot tonearm " means ".
In the other side the levels of IMD in your system is just to high to detect real limitations/advantages. Why? ( I take the information from your published  virtual system. If already changed then my comment is out of focus. ):

those 800 speakers comes at least witjh two issues that goes against top quality performance level: exist in the music signal information an equalizer/filter where that signal information is degraded and if that device is not used then low range speaker response can't meet B&W specs.

In the other side those 800 woofers handle from aroun 300hz and below it incrementing the IMD aside that the FBP 600 was not designed to meet exactly and cope with the specific woofers characteristics. Here you can read about:

https://forum.audiogon.com/discussions/do-you-think-you-need-a-subwoofer/post?postid=310058#310058

If in the future you make a test in your system integrating two active subwoofers in exactly what I posted in that link you will be nicely surprised. You say you are willing to learns, well this is an unexpected opportunity where I'm totally sure you will have NO comeback/NO return after test it. 

Anyway, till today I don't need to change to LT tonearm design so why bother about?, I don't care about and as I said: " AS is not what can makes the differences between both kind of tonearm designs.

As I told you if you are happy with your LT design good for you, I prefer pivot tonearm design.

Regards and enjoy the music,
R.