Darin’s right but you have to remember the glow goes both ways, especially at low (relative) engine speeds. So reversion can become an issue if the cylinder pressure is still high when the intake valve opens during overlap. The cylinder needs intake charge. Not something diluted with residual exhaust gasses.
If it’s a factory design port and lift expectations are moderate the back cut will help a lot. With a properly designed aftermarket port and larger lifts the effect is less dramatic and reversion can be more of an issue.
