Wow! Thank you very much, "2uesday"! This piece is overflowing with all kinds of real information - and the explanations I've unfortunately found neglected wrt anything "tech".
They did give a suggested range, and yet another for an info piece. And yeah - they did opine that much more than 20 is probably overdoing it, and might even set off the "stuffing" alarm and get Google all in a huff!
Thank you again for a great answer via an *awesome* link.