Regarding incidence, reaching back into some really old (thus questionable!) memory banks, my bet would be one of 2 reasons. First, 0/0 is used for more performance applications. Has more of a tendency to go where you point it, like pattern planes.With a Sunday flier type mission in mind, thinking they wanted to make it more forgiving, maybe keeping potential speed limited? Second, could also have something to do with the airfoil's performance. Might just work better at 1+, using the logic Jim wrote about?
Been a long time since I even thought about stuff like this. Used to be a big factor when building from a box of sticks with performance in mind. Today's ARF's generally don't even specify incidence.... -Al