Snitch,
I believe that there is a section on TEs in AEROSPACE VEHICLE DESIGN, AIRCRAFT DESIGN by K.D.Wood that says exactly what NACA says about this topic, that sharp was best, small but squared was next, round wasn't good and thick was bad. Obviously, not in those words.

I tried to find it today but the book has a lousy Table of Contents and worse Index. But the author is an Aeronautical Engineer after all, so you'd expect that right?