Generally, it’s okay to run 0.5qt over the full line. Some people run 0.5qt over on purpose because they’re racing and need the oil pressure during hard cornering.
My 03 Cobra calls for 6 Qt’s. I always run 7 Qt’s. The slow drainback from the heads along with my larger capacity oil filter allows me to get away with it. But I would not make habbit to do it on other cars. Along with that, When hard cornering or racing
my maxima calls for, I think, 4.2 quarts of oil. I just put in a 5quart jug in every oil change. no issues whatsoever. and the head gasket must of been bad luck. I can’t see how too much oil could damage it.
I found it is better to run the level a little low, otherwise it seems to burn off the excess like adding 1/2 bottle every day or not adding any and it will stabilize between the normal marks… My Toyota takes 3.2 qts and I fill it with 3 qts and add 1/2