LouW

As noted in the drag curves in my response above, it doesn’t take much camber to put the drag bucket in a most favorable position to cover both straight flight and steep turns. Everything else being equal, in positive “g” flight, a little camber always results in a more efficient wing. I think the prevalence of symmetrical sections (if that is the case) is a carryover from aerobatic design where inverted flight is a given. That is really the only place a symmetrical airfoil is the best choice.

(Whether some existing symmetrical airfoils operate in the drag bucket during steep turns is largely a matter of speculation. Moving the bucket to a higher lift coeficient would certainly increase the margin and might allow a little tighter turn. Every little bit helps.)