It's not undisturbed air. On my ex Stemmes , serial 11-18, the nose TERRY was severely under compensatedevelopment due to the bow wave. I increased the TE "washer" size to 3/4" IIRC and that helped a lot. Other Stemmed owners followed suit and agreed. Stemmes did not come stock with fin mounted probes then, some owners got them when the issue became known.