Remove the cabochon, and note the height of the mark. I used a Fine Point Sharpie marker, which still gives a fairly wide mark. The top of the mark is equal to the highest 'top' of the stone. Since you only want the bezel to slightly overlap the edge of the stone, choose the lower edge of the mark to make your measurement.
Since the stone was sitting on the wire, you must measure from the top of the flat wire, to the bottom edge of the mark. Measure in mm's to get the most accurate measurement. A ruler whose measurements begin at the very end, rather than 1/4" or so away from the edge, is most accurate. If your ruler doesn't 'begin at the end', you'll need to untape the wire and hold it while you measure. Use this measurement for the height of your bezel.
Congratulations! You're ready to start weaving!
Refer to my article "Three Ways to Keep Your Weave Railroad Straight", for help in maintaining the measurement as you weave.
We always welcome suggestions for new articles.