Thanks for the responses all. This wasn't the actual aritcle I was thinking of but it looks like it has what I needed - thanks. My LF lenses are all Symmar S at the moment so it works for me. (I say "all" - it's a 90mm and a 210mm!!)
Re the DoF and focusing 1/3 into it; I'm pretty sure that with the bellows set half way between the two "extremes" of focus you are indeed focused one third in, two thirds out - at least that's what I recall from the article I had in mind.

thanks very much again guys.

Bob H