Well I did some testing with this mod



From results so far the engine loses power in the upper end

First the engine was tested with a normal button, then the engine was tested with the grooved head button... then I decided to raise compression slightly to compensate for the cuts...... The engine did gain back some of the lost power with the raised compression, but still not as good as the stock head button

yellow is stock head button
red is cut head button on its own
Blue is mod head button plus reduction of head clearance 0.05 mm