Won't be able to measure until the 16th. Perhaps somebody else has this setup.

Basically, its pretty close to the middle. I don't think exact position is critically important as long as it matches up with the block on the middle of the boom. If you right click the pics on the 1st page of the thread and open in a new tab, you might be able to zoom in a bit more and get a good idea.

Will post an update when I set up for our first regatta on the 16th. Can't wait!!!