Micheal Selig was working with really fine differences and I would guess that getting a wind tunnel smooth enough to do it was a real chore.

The big tunnels we used at McDonnell Douglas (I spent half of the best years of my life testing models in them) probably have higher turbulence but also were bigger and have much wider ranges of velocities.

I have often thought that it would be interesting to put a pattern model in one and look at the data but after several thoughts more realized that our models are so simple that it really isn't necessary.

Complex configurations with slats, flaps, differential tail and ailerons, external weapons or tanks make theoretical calculations suspect. That is where the tunnels are worth the time and effort.

Like BMatthews I tend to use little foam models to determine CG, etc for airplanes that are off the beaten track. Luckily most airplanes that fly nicely have a lot of characteristics in common and it makes the job of estimating what they can do easier.