"Joe Gwinn" wrote in message
...

Hmm. I will remeasure the Vee angle. These measurements are a bit
clumsy to make, and errors are a danger. I think I'll try some
variation of the two rods (different diameter penetrates to
different
depth in the V) approach.

Joe Gwinn

You could trim a small piece of sheet metal to nearly the correct
angle, press the straighter edge against one side of the internal vee
and scribe a line parallel to the other side.

Measure it, construct a more precise sheet metal template at the
suspected angle with a vernier protractor, and see if it fits
light-tight.

Can you tell that I have many years of experience making precise
measurements with office supplies and rinsed-out soda cans?
jsw