I believe the change Potter made from Moesly's original 4 stringer design to the 2 box stringers was primarily a cost reduction because it would require less glass and resin, and the change occurred in '73-74 after the first Arab oil embargo when the price of oil, gas and resin went up by 2-3X!. There is no way it can be as stiff as the 4-stringer design, but the fact that it works simply indicates how overbuilt the original Moesly design is! Moesly started out by building the old 21 as light as he thought possible and then raced it to intentionally beat the hell out of it to find any weak spots. Not only did his boats finish races in weather so severe that it destroyed the boats of many competitors, the 21 dominated the outboard classes, so I don't think there were any weak spots! Moesly knew from his racing experience what worked and what didn't. Potter had no boat building experience before he bought the company from Moesly, so whatever he knew he learned from Moesly during a couple of years of working with him before taking over the company. Although I've never heard of a structural problem on a Moesly boat, there have been some rare quality control problems documented on here on a couple of Potter boats - a loose stringer on a 23 and some hull cracks on a 25 Seafari in an area that wasn't built with the ballast tank the way Moesly had designed it.
I believe the scuppers on the Moesly 20's run out the transom instead of down through the bottom, and he may have crossed the drain lines under the deck so port scupper drains out stbd side, etc.
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