My personal view (on the general topic, not directly in response to
gimp):
On the general issue of exactness in positioning, my view is that the
rules provide guidance on positioning to help players resume the
important part of the game -- playing the game. The rules help both
teams get a fairly good sense of where the disc is to be put into play
and the fine-tuning can and should be done by mutual agreement.
Whenever I am putting a live disc into play, I ask the marker as I'm
approaching the spot, "is this good?" or something similar. We agree,
I stop, touch the disc to the ground, and begin playing. This
procedure consistently works well on lined and unlined fields.
The fact of the matter is that we don't have geometrically perfect
fields and the determination of where a disc crossed the perimeter
line often involves a substantial margin of error. Players should
make an effort to reach agreement on where a disc is being put into
play to avoid confusion and unnecessary stoppages. Following this
procedure, the "wrong spot" travel call should be extremely rare.
Purposefully avoiding reaching agreement for the purpose of later
asserting disagreement with a travel call is cheating.
More specifically addressing the exact positioning of the pivot when
carrying the disc to the playing field proper and putting into
play... In my view, calling any travel for a misplacement of the
pivot within the length of a blade of grass is absurd, unless the
caller has inspected every painted and unpainted blade of grass at the
spot in question AND can confirm exactly which blades of grass the
pivot is touching.
The rules (XVI.A) say that "an infraction may only be called by a
player on the infracted team who recognizes that it has occurred." A
player on the allegedly infracted team who recognizes that an
infraction might have occurred is not allowed to call the alleged
infraction.
I think the Golden Rule is helpful:
Do unto others as you'd like a whole teamful of opponents to do unto
you and every single one of your teammates.
-Colin