How about those straight arms that must have been 2' long on  RCA transcription turntables ?
With a pick up that would play vertical and lateral  and a conical  stylus  it would appear that  any tracking misalignment  would be nominal and have little effect on playback response.
No one has mentioned these and like long arms......  Astatic  even made a straight arm that was at least 12-14" long.

 From: Nathan Coy <[log in to unmask]>
To: [log in to unmask] 
Sent: Saturday, December 17, 2011 6:41 PM
Subject: Re: [ARSCLIST] Straight Line Tracking was Stanton Turntable reviews....anyone?
Oh here we go
I guess I'll have to find a copy of the Radiotron designers handbook
mentioned here.

sorry all,

On Sat, Dec 17, 2011 at 8:13 PM, Nathan Coy <[log in to unmask]> wrote:

> I've been following this with great interest and as a byproduct have
> wondered about the differences between carefully compensating by angling
> (in respect to radius of disc) a cartridge in the headshell on a straight
> tone arm vs. a curved tonearm with same cartridge angle. This is assuming
> that both tone arms have the same effective length and are of course
> radial/pivoting and not tangential arms. I've been digging through the AES
> E-library a bit haven't found any article covering this specifically with a
> discussion of comparative distortion at select imperfect angles (although
> have now read a lot on anti skate design, tone arm weight, rigidity, etc.).
> I did come across a quite old article that's pretty interesting though and
> close to what I'm looking for:
> Carlson, R.E. (1954). Resonance, Tracking, and Distortion: An   Analysis
> of Phonograph Pickup Arms. Journal of the Audio Engineering Society. 2(3),
> 151-162.
> especially pp. 157-158.
> I've seen statements by companies saying s bent arms are better but I'd
> like to see the documentation/detail.
> Any direction to sources would be appreciated along with discussion  here.
> Thanks,
> Nathan Coy
> On Sat, Dec 17, 2011 at 3:18 PM, Graeme Jaye <[log in to unmask]> wrote:
>> On 17/12/2011 Andrew Hamilton wrote;
>> AH> I think Mr. Jaye meant to say "tangential tracking arms."   However,
>> the
>> AH> tangential trackers do move along the radius of the disc.  (: Better
>> AH> maybe to call the straight and S-shaped arms, pivoting.
>> Sorry to have confused anyone.
>> In my original post, I actually referred to "a radial tracking system"
>> - which means, of course, a linear tone arm (and tracks along the
>> radius of the disc, as you rightly say) - not a radial tone arm.
>> The main thrust of my comment was that Goran Finnberg had actually
>> confused the original question (which concerned the differences
>> between straight and curved radial tracking arms) with linear trackers
>> and went to great lengths to prove that he was right (which he was)
>> although not understanding the question.
>> Graeme Jaye
>> [log in to unmask]
>> Audio Restoration and Location Sound Recording