My plugs have the strap filed down even with the middle of the electrode, which opens it up halfway but still allows the spark to wear the electrode somewhat evenly. Also beveled the end of the strap to make a much sharper edge for easier arcing. I have no idea how much it helped since I put them in a newly rebuilt motor, but I don't think I saw much benefit because I don't have the plugs indexed which kind of defeats the purpose of opening it up.
Instead of dicking around with plugs you could buy those Bosch Platinum2 plugs. They are side gapped, but platinum electrode for long life.