Pattern designs for years have used a "compromise" airfoil. Dick, you can likely support me on this and fill in any holes since I sure don't have your background in pattern models.

As I read different arcticles about pattern models over a number of years in the old model magazines it soon became apparent that they did not want the airfoil to perform TOO well. Just well ENOUGH. It's a fine line between a model that flies smoothly and turns well in pitch but that can snap roll cleanly on demand. "Detuning" an airfoil by sharpening up the leading edge or selecting a less than ideal choice from a low stall speed standpoint was done often to get the model to achieve just the right charactaristics. And as the focus on the style of manuevers shifted the choice of airfoil shifted along with it. Now we have 3D models that use a much thinner airfoil with relatively poor, by normal sense, stall charactaristics. But they are the right tool for the job the model is designed to do. But this choice presumes that the maker will be able to meet the rest of the criteria to let the package fly as it was intended. So along come a bunch of ARF companies or builders of kits that don't know that the model needs to be kept down to a target weight and suddenly we get lots of compaints about models that stall and snap roll when doing loops or during landing approaches.

The point is that a "proper" airfoil IS a very highly subjective call in a lot of cases. In other flying tasks it can be more sharply defined but even in those cases there's seldom a single track, single solution. Look at world class F3B sailplane designs. There's gobs of slightly differing airfoil choices that put just a hair of emphasis on different aspects. Even commercial airliners have a number of various airfoil and flap options yet all seem to manage to top the bar that is set for them.

Anyhow, back to dimples. If it's true that those Cessnas did gain some top end then it's because the surface finish or the choice of airfoil was less than optimum for top speed use. It still comes back to the idea that using turbulators is a "bandaid" for a bad design or to fix an issue at some point where the gain gives back more than the cost in other modes. In the case of the golf ball the shape is mandated and the dimples are a fix to get more out of it. With an aircraft the pluses and minuses have to be weighed and a decision made to use turbulation or change the airfoil design to achieve the goals without using add on fixes.

In some cases the cost enters into the issue. The old A-4 Skyhawk uses outer tip turbulation to delay the stall at the tips or to gain some aspect of this sort during high G loads and during landings. The Aermacchi Delphin uses the same style turbulators on the lower leading edge of the stabilizer to gain more "lift" or lower drag or better control stick feel during larger applications of up elevator. But both of these gain what they get at the expense of adding drag. Perhaps both would have gained more by switching to a different airfoil or going with an alternative airfoil modifying device such as leading edge slats. Or perhaps not. But doing so would definetly have cost a lot in terms of time and money.