Maybe it would not be too expensive to build up a wind tunnel. At least most model airplanes are smaller than the models used in the aerospace industry for such testing. You'd only have to make the space wide enough to handle one wing and the fuse. You could leave the other wing off. Another way would be to mount your model on top of your car and use the corn starch/fine powder method and maybe a video camera. You'd just have to do it some where that to avoid a speeding ticket. So far I have discovered that a lot of common knowledge about aerodynamics is just plan wrong or at best incomplete.