Bigger is not always better! A bigger valve will get closer to the cylinder wall, which will restict flow. A bigger valve will allow for a bigger valve seat throat which will pass more air, but not necessarily better air. Same is true for the the entire port: if the air speed is too low, the kinetic energy will drop and as soon as it returns from BDC (bottom dead center), the piston will start pushing back the fresh mixture sooner. Bye bye midrange.
However, even when the bigger valve does not improve flow because of the increased cross section, it involves removíng material which gives the opportunity to modify the shape of the inner radius of the port. Make the airflow keep the apex. So maybe we should keep the slightly oversized valve anyway, and create a venturi in the port to regulate the air speed? But where to place the venturi, having which diameter?
There we have our first achievement: we are not chasing bigger holes anymore. Instead, we target for a section area and try to improve the shape to get more air at the desired speed. Negotiate with the flow. At the highest levels of diplomacy. This is not our yearly trip to Davos but our daily research at the flowbench. Inhouse, for more than 25 years. You could rely on it, too.