Obtaining accurate predictions of aircraft aerodynamic coefficients from wind tunnel tests is a difficult task Wind tunnel users have struggled with the effects of wall interference, model support interference, subscale Reynolds number, etc for almost the entire history of powered flight Since wall interference is one of the principal problems this paper emphasizes the need to minimize it, especially in the near sonic test regime Practical ways of minimizing wall interference are identified This is best accomplished for near sonic testing by locally variable porosity with inclined hole perforations A number of porosity setting schemes are identified some of which are quite simple