Tuning pin angle(s)

[jimialeggio5 at comcast.net]

List,

In searching the archives and reading whatever info is available
in past journals etc,  reasonable consensus is that the string takeoff
angle from the pin centerline to the counterbearing bar should be around
90 deg.

A couple of questions regarding this:

1-in looking at a number of plates, particularly ones with the "ski slope/very 
minor counterbearing bar/lots of felt contact ", the pin angle in relation to 
the webbing would have to be a negative angle to achieve 90 deg string takeoff 
angle from the pin. That is negative, ie  actually angled towards the belly, 
often by 4-5 deg, assuming coil height at 1/8 " from plate.

Is 90degrees takeoff ,90 degrees, irrespective of the orientation to the webbing 
(or actauly the rim top which indexes many rebuilders drilling jig)?

2-the difference in takeoff angle between the front pin of a unison and the back 
pin of the same unison results in a very different takeoff angle, maybe 2-4 
degrees.

90 degrees can't actually be 90 degrees throughout, unless you're nuts.

3-the 90 degrees(or so) is not in relation to the stretcher, but in relation to 
location of the agraffe, which again changes from note to note. Does anybody 
actually customize the direction of the angle from note to note?

4-Regarding the "ski slope/very minor counterbearing bar/lots of felt 
condition"...rendering the string over all this felt creates problems because of 
the tendency of the wool to hold 
moisture, and rust the string/felt contact. 

??Why is wool felt exclusively used in this place?  Besides the obvious reason 
which is "because that's the way its always been done".  Some rebuilders do 
infact use acrylic felt here, but keep it quiet in the fear that they might be 
struck by lightening if anybody knew their dirty secret.  Any thoughts?

Jim I