Going 8s on carbs is different than setting up carbs that are going to be used for spirited cruising, I'm sure. You're getting pretty defensive about your answers, when nobody has said you're wrong in any way... we're just suggesting other things to consider.
Cruising is done on the main circuit, airs richen or lean the mains in the uppermost RPMs. Emulsion tubes and etc. will determine the richness on the main tubes at cruise as well as the choke size. To me his problem sounds like the changeover from the progressive circuit and main circuit has a lean spot. Obviously he's not cruising at the same RPM and then it suddenly bogs out and then goes back to normal. It's probably experienced when he's speeding UP TO a cruise speed, which he would go through the changeover in circuits. If the jetting was fine previously, and you're experiencing this condition randomly, I would definitely check the plugs and maybe even the fuel pressure. Bowl floats could be getting stuck and not filling the bowls correctly, as well.
http://www.tr3a.info/TR.images/DCOEchart.jpg