You're right, of course - I was trying to handwave an "even if there's notable contact resistance along the way" without thinking at all seriously about probable values for same.
Again "d'oh" applies - thanks for picking it up.
Paul Cook couldn't've put it better ;-) Now, whether it's got too many Numbers, Equazhuns, and Square Roots to be circulated as-is in NICEIC helpful-hints is another question.
Stefek