well, for me it's

too...
let's take a look at the text quoted by Doug, (the radical example):
10.5 inch tonearm, 0 overhang, 5? of angular offset will not lead to a zero error at the innermost grove. The innermost groove on a lp, stated by IEC standard is a 60.325mm from the record spindle center.
http://www7a.biglobe.ne.jp/~yosh/recspecs.htmThe innermost groove considered by the "tool" is at 1.875" (1 7/8) that is 47.625 mm - If you find me ONE LP with a groove at 47.625mm from the spindle center, just tell me, I'll pay you a bottle of (French) wine.
At 60.325mm, the groove tangent is at 6.486? and the error is 1.486?
At 47.625mm, the groove tangent is at 5.117 and the error is 0.117?
At the outermost groove (IEC standard=146.05 - same value on the "tool"), the groove tangent is at 15.878?, (not 17?) the error is 15.878-5=10,878?
on the wtl blog, the specifications of the amadeus tonearm are finally indicated : overhang = 0.5" and angular offset=19?
associated with an effective length of 267mm, that will produce null points at 56.34mm and 117.52
distortion values across the record forced by this value are "fair" since the arm is rather long (but far from being optimized...)
Now, if you take a look at the amadeus protractor, here :
http://welltemperedlab.files.wordpress.com/2009/02/tonearm-alignment-guide-for-amadeus6.pdfthe (unique) null point is positioned at 1 7/8" = 47.625mm (the supposed innermost groove), not at 56.34mm
william firebaugh said he read the Stevenson (1966) paper :
http://www.vinylengine.com/phpBB2/viewtopic.php?t=11568this paper is indicating that the inner null point should be positioned at the inner most groove (because the closer you are from the record center, the more a given tracking error will produce distortion). The inner most groove is given by Stevenson at 2 5/8" but William Firebaugh considered 1 7/8 - an error in his reading of the stevenson paper ? (badly scanned, I know....). Nevertheless, William should take a deeper look at a LP...
To me, (this is just an intuition), william firebaugh made another mistake. I'm quite sure that he's considering the angle formed by the straight arm tube and the cantilever as the offset angle - that angle is not the offset angle since the offset angle is the angle formed by the line passing through the stylus tip and the axe of the tonearm (at the golf ball) and the cantilever.
IMO, this is what happened at the WTL factory:
"guys, we need to propose a new turntable but we're having a problem: the average guy doesn't like to set up his cartridge - he thinks it's too complicated and it would be an advantage if we could propose a very simple way to set up the cartridge"
"boss, you're right"
"so, to me, the best way is to propose a fixed headshell with no slots a la SME old school but with no sliding base"
then William talked:
"but, the average guy is knowing that it can not be that simple - he'll think there is a problem and won't trust what we'll propose"
"no problem" said the boss, "we'll explain him we found a new revolutionary way of thinking of the problem - just find justifications based on second order harmonics, quote old papers, look serious by proposing super complicated tools and say that the others are wrong"
"ok" said William "I'll do the job"
best regards
Seb