Is my anti-skating too strong.

A high effective horizontal mass means that the arm will not swing side to side from the needle tracking the wide modulation of the groove (the full groove swing will be translated to movement of the cantilever instead of some of the movement lost to the movement of the arm).

Perhaps you could explain why it is imperative to have the cartrdge swinging around whilst trying to measure the groove. Have you ever tried to accurately measure the height of your ceiling whilst jumping up and down on a trampoline - you can't. 

It is NOT ideal to have the cartridge moving.  You want the cartridge position to not change so that the full motion of the needle swinging side to side is transferred to the generating element of the cartridge.  If the cartridge moves, the amplitude of the signal reaching the generating element is reduced.  That is why high effective mass (high inertial mass) reduces the tendency of the cartridge to move in response to large bass modulations.  

Moerch  makes an "anisotropic" tonearm with large outboard counterweights located at the vertical pivot.  Because of this location, the weights contribute little to vertical mass, but, they increase horizontal mass for the purpose of improving bass response.  I've heard this arm and it does have a bigger bottom end than typical arms.  I also thought the bottom end of air bearing arms seem particularly full, but, I have no way of attributing this to the high mass.

I personally agree with you that excessive horizontal mass is quite undesirable.  This probably puts a strain on the cantilever/suspension of the cartridge and might even cause uneven stylus and groove wear.  I have never heard the Shroeder LT or the Reed T-5 arm, but, I really do like the engineering concept behind those arms.  They seem to be the best way to maintain proper azimuth without causing other problems.

Horizontal effective mass is 25-35 gm and vertical is 7 gm. A normal pivoted arm might be 12 gm vertical and 13 gm horizontal. 20 gms is much to wide a divergence.

You miss the point I made earlier - the effect of splitting the horizontal and vertical effective mass is an advantage - vastly reduces the fundamental peak resonance in amplitude. In a conventional arm the vertical/horizontal resonance are the same and the peak amplitude from the fundamental resonance is cumulative.  By splitting the horizontal and vertical effective masses you have 2 fundamental resonance peak amplitudes that are not cumulative becuase they occur at different frequencies. Whilst the fundamental resonance may be out of the audioband for most systems, If you look at the Shure white papers, the fundamental resonance can be devastating to accurate tracking and distortion and has significant artifacts within the audio band. 

Tracking error is not near as much of a problem as it is made out to be not that minimizing it is not a good thing.

Really - check out how many folk have offset/bent cantilevers within a short period of time - its well north of 50%.

So, the discussion has come around to the idea that high effective mass in the horizontal plane, relative to vertical effective mass, is at least theoretically a good idea.  How does one know that 25g is too high?  What is the typical horizontal compliance of most cartridges?  While reading the preceding posts, I remembered that some pivoted tonearms place outboard weights right at the pivot point, extending out on either side at a 90 degree angle to the arm wand.  These weights are added in order to increase horizontal effective mass, and I have read at least one thread, a few years ago, wherein the benefits were said to be evident.  M Fremer has popularized the idea that horizontal mass should not be so high, for what that is worth. It seems logical to me that when the stylus is trying to trace the heavy horizontal modulations of a bass response, you want the stylus/cantilever to move whilst the arm stays as still as possible. 

lewm,

You are describing the Moerch anisotropic arm I described above.  I think the model is the DP8 or DP9.  

I have no idea if 25 gms is too high, I just know it is WAY higher than is common with conventional arms.  In the past, some users of air bearing arms reported snapping the cantilevers on their cartridges (Walker owners, I believe), but, who knows whether there is some other cause for such problems (its not like user error is a rare phenomenon).