I followed the same procedure as I used to mark my test waterline earlier (see page 2).  I began amidships, bringing the string in at a predetermined and equal point on each side of the boat, and taped the string where it touched the hull.  Because the black marker wouldn't show up on the dark blue hull in this area, I marked the string height with a short piece of tape, applying the tape just below the string.  Later, as the string entered the white old boottop, I returned to using the marker.  

I marked the forward half of the boat first, following the same procedure as before--pull the string in towards center till it touched the boat 4" - 6" away from the last mark, then tape it place, mark the line, and repeat until the string touched the stem.

To make it a little easier to mark the complicated curves of the boat beneath the counter, I found that it helped to remove the tape holding the string into the bow sections, leaving it taped only amidships at maximum beam, and bringing the forward end of the string further outboard on the horizontal support to ease the tension on the string as I pulled it in beneath the counter.

When I had one side completely marked with the string, I removed it and applied masking tape to the hull, following the top edge of the pen and tape marks.  I faired the line by eye as I applied the tape, and didn't try to hit every mark exactly, concentrating instead on every other mark or so.  When I was satisfied that the line was right on the first side, I repeated the entire process above on the other side of the boat.  The silver tape I used is 3M #225, a 30-day release tape that I really like for virtually everything.  It never leaves adhesive behind, stretches nicely, is strong, and allows for a fine paint line too.  It's pricey as anything, but well worth it.

The counter is by far the most challenging to mark and tape.  The string, when pulled in and taped as described above, was fairly accurate, but this tape line still required much fairing by eye, checking it  from several different angles and eye-heights, particularly with the eye on the same plane as the line.  I used blue tape for this because it's cheaper to pull off and start over, and I only had a limited amount of the silver tape on hand.  The height of the camera is a bit off in this photo, but it attempts to capture the apparent straightness of the tape line under the counter.  Of course, looking at it from beneath shows all the various curves required to get this optical straightness.

Here are the new tape lines (in which the new height of the antifouling paint will be brought to the bottom of the tape) seen from the bow and stern.  The port side beneath the counter is still a little off to my eye, but I'll correct that on another day.  In visualizing the new line, it's important to ignore the old boottop and bottom lines, which are irrelevant to the new line.  Still, their presence tends to lead the eye astray and fool it into thinking the new line is funky.

Because of the difficulty in properly visualizing whether the new line is "right" or not, I needed some additional confirmation.  After eyeing the thing from left, right, backwards and forwards, I decided to compare it to the original, as-designed waterline mark--the lower scribe mark, now mostly covered with bottom paint.  There was enough of it visible, however, for me to run tape lines along it on both sides. 

In doing this, and wasting 65' of tape, I wanted to confirm two things:  that the original designed waterline was indeed planar, like my new one will be; and that my new line appeared to be parallel to this original one, 5" beneath.  I was happy to see that my new line did indeed parallel the original designed waterline (DWL).