I understand how it works, and that it lowers the height by the thickness of the blades you use, but anyone who is paying attention to what they are doing should see that and adjust their HOC stop accordingly so that the HOC corresponds with the lower blade tips at the front of the deck.
If anyone else is interested, if you go to Walkers youtube
site, they have a video showing the use of doubles on their mowers. They are another company that uses the manual pto still. At 1:50 of this video, the operator tips up the deck giving you a clear view of the double blade setup.