My zero diplomacy response...

: I read a step-by-step account posted by someone who built a Pygmy Osprey from
: a kit. Upon checking the vessel for trueness, he said it was within a
: thousandth of an inch over the entire length.

It was probably in his dreams. To rig a rock solid, multi-axial jig to sample a series of sample points would itself be a daunting multi-day task, to have the exact cooridinates in whatever scaling of those sample points would be impossible.

: How did he determine that????

: I am beveling the long panels of a Merganser-to-be and expect to wire the
: pieces on Saturday. Part of the reason I went with a wood kayak is that my
: present kayak, which is plastic, has a slight curve to the left that
: drives me nuts. (Guess which way it tends to go.) I want to make sure I
: get everything properly aligned before I commit to the glueing, as a
: friend warned me that some people he knew built boats with similar
: problems.

First of all, since I'm watching over the construction of a Merganser 18, the building is pretty much straight forward. One thing, a tenant in building anything. If it looks good it must be good. So what you should do is trust your eye, which is capable of detectig the smallest variation. Sight down the center line and see if the form is symetrical. You can lay out a line over the center line of the hull and from that measure a 90 degree distance to either hull edge to determine warps and the like. I wouldn't worry too much.

You can fix that plastic boat by heating and bending back the bend, of compressions, or the like. The HDPE plastic is able to be 'molded.'

: Someone mentioned a laser level. A quick search on the net turned up a huge
: price range ($20 to $500). Are accurate ones available for rent? I don't
: want to buy one just for a one-time task. What alternatives for checking
: alignment are there, besides eyeballing the boat? (Yes, I am a total
: rookie at making anything.)

What's the point, where would a level help? You can rig something easier and serve the same purpose (see above) to measure the distance from one hull edge to another if your eye is telling you there's a problem, otherwise, any minute variations are so minute as to not matter.