Kirk;
You got me thinking (not an easy thing!!).
I got out the old straight edge and assumed my tying position. Keep in mind that I use a lighted magnifyer, My eyes are about 10" above the vice and the distance from my eys to the vice are about 12". I guess I'm looking down at the vice at about 20 degrees.
Seems like this has me sitting up straighter.
I also only tye a few at a sitting. How many depends on how many thumbs I have.

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Cactus