Defining the start line with start marks

The racing rules allows for fair competition, but it is a challenge to understand every scenario. To help facilitate the process, the Racing Rules of Sailing Forum offers an opportunity for experts to voice opinion. In a post by Doug Ryan, he was asking what part of the starting mark was the official end of the starting line:

We have a round ball as a starting “pin”. Looking down the line from the pre-start side of the RC flag staff, a boat had its bow directly in line with the center of the “pin” ball.

Is she OCS because she was over the line to the pre-start side of the ball? Starting clear because half the ball was still visible when the start horn/flag was sounded/dropped? Does the RC need to sight to the middle of the ball which is the hardest position to actually determine?

Curious as I have not faced this situation before. We can find nothing in RRS on this and there are no appeals we can find as OCS is not something you can protest. Interested in your thoughts.
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Here were some of the comments:

Greg Dargavel, National Judge:
It is your SIs job to define this for you. Usually it is defined as the course side of the object serving as pin.

Roger Strube, National Classifier:
“In theory, theory and practice are the same. In practice, they are not.” – Albert Einstein
On the course side is the operative wording. “The course side,” in practice, is the part of the mark usually to windward the RO can see (or estimate at the start of an offshore race with 6′ seas running), instantaneously at the starting gun/whistle. This is an eyeball, judgement call, sometimes made on a very unstable platform, in less than two seconds. If the RO, with her/his eyeball on the signal boat line flag staff, sees any portion of the mark at the gun, the boat is not on the course side. If the mark is covered by the bow, the boat is on the course side, “over the line.” Don’t blink.

Matt Bounds, National Judge and National Race Officer:
Tetrahedrons – with a constantly changing course side / non-vertical aspect as they rotate – are less than ideal as starting marks. Cylinders or spheres (“tomatoes”) are much better. An anchored boat with a flag/staff is the best – plus you have another set of eyes on the line.
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