Cornball or not use the method that works best for you, a millimeter scale on a monorail makes it very easy for me. For my 120mm Nikon for example, I set the film plane 120mm from the lensboard, then note the distance on the monorail from inside to inside of the front and rear standard (30mm in this case) or outside to outside, does not matter. I've calculated what the BEF is at 13mm intervals (half inch) for several inches of bellows extension. Only after I have achieved final focus do I think about any possible extension, I quickly look to see if the inside to inside distance between the standards is greater than 30mm, if it's 56mm for example, then I know I have extended the bellows, just look at my little table and note the factor for a bellows extension from 30mm inside the standards to 56mm---------a one inch extension, +2/3 stop or 1.5x in this case---very quick. It only takes a few minutes to work out a small table for each lens that you have.