Design constraints, ideally you would want a multi element wing, with the main element as high as possible with multiple slots towards the end plates, and a lower element who's wake is adding to the rear wake of the diffuser. Also adding serrated turning vanes to the diffuser will increase the stall limit and reduce pitch sensitivity.

 

My impression has been that the "neutral" center section is an attempt to maintain somewhat constant attack angle across the wingspan. The air coming over the roof attacks the wing at a different angle than air flowing along the side of the cabin and the wings are shaped to maintain constant attack relative to incoming airflow. As you increase overall wing angle, a straight wing will stall in the center sections prior to the edges unless it is mounted above cabin height or really far back, both of which are often regulated by rules in competition.

 

"both of which are often regulated by rules in competition. "


That was my main question. As just an HPDE junkie I get to 'run what I brung'. I know most series people in this forum participate in tend to limit wings height and width (or else you jump to a new and undesirable class). I don't recall reading much though on rules regarding how far back the wing can be mounted.