Hello Don,
Here are quotes from Michael Yardley's book "Gunfitting: The Quest For Perfection"
for your reference:
"Correct stock length can only be precisely ascertained by shooting targets".
"The nose and finger method -which, again, has its uses if its limitations are recognized- goes wrong most notably when incorrect head placement on the comb gives a false impression of the stock length requirement".
"Another point concerning fitting for length is thickness of clothing".
It must be said that Yardley does have a try gun on the cover of his book,
which is not your case, but surely more advice will come along to help you
define the length you need.
JC
