Teeth greatly impede surface skimming. That said, it really depends on the livestock, linear overflow length and flowrate. Small overflow with high flow will tend to allow too many fish to take the trip to the sump. Teeth help to prevent that, but (again) severely limit the surface skimming. The answer? A longer overflow, of course.
Building it myself out of glass. Did you think 3/16" is sufficient?What confused me was the description of "extending the sides". I now caught that you are building the tank (or having it custom built). Out of glass or acrylic?