Ty, to your #9(?)
Billy W explained his bulgy flaps in a article within the past 5-7 years, possibly an update on his Juno in FM, or Junar??
He considered them when they pull max deflection. The "upper" surface (in the direction lift is being pulled) fairs better to the airfoil than a flat-squared flap, or a to-a-point tapered flap. It was deliberate, and (for him anyway) it worked. Or so he believed, and with his results, who's to argue?
(How many times over the years have you caught me saying that precise scientific accuracy isn't what counts, but belief by the flier IS?)