By stock airfoil I mean exactly that, the airfoil that the full scale aircraft was carrying when it left the factory. From my auto racing roots I refer to things that are the way they left the factory as "stock". Some early airplanes had undercambered airfoils, some later airplanes have flat bottomed airfoils like the Clark Y. Many WW II fighters had airfoils that lend themselves to aerobatics. While not fully symmetrical they are a very long way from flat bottomed. My Profile Scale Extra 330 SC has the fully symmetrical airfoil that the full size aircraft carries. That should make it competitive with most any non-flapped stunter. Some of my designs that are intended for Profile Scale competition were originally offered with symmetrical airfoils. Many of those have been updated to carry the same airfoil as the full scale airplane to prevent loss of points in national level competition.
My profile P 47 stunters are profile versions of the Bill Werwage World Championship airplane. They look like the full scale airplane, but would lose points in static judging for Profile scale. Those airplanes are designed to fly the full pattern. In most cases I am not trying to produce models for flying the pattern in competition. Many of my Fun/Sport airplanes have fully symmetrical airfoils that will perform stunts well, but not at a competitive level.
Pat