Wow!! I haven't heard those two gouges for DECADES !!! What's that tucked under your arm?? BOWDITCH ???
The 'true virgins' was always our preferred choice, of course ... for a variety of reasons. It's nice to be a fly-boy instead of a BOAT driver sometimes so you can basically dismiss deviation ...... and of course, being WestPac sailors, we'd throw in 'West is best, East is least' for the +/- gouge ...
Here's an interesting, if slightly involved, article on some of the thinking behind how the ol' boys used to do it ... from the forum: DEAD RECKONINGS
COMPASS SWING, anyone ... ???
Not so sure I buy the fact that you have dismissed deviation!