Yes it is overkill.
However, I have run Amsoil 10W30 motorcycle oil (MCT) in my air cooled, Subaru Robin powered, 10,000 watt generator before. Also, my Kawasaki powered Cub Cadet Lawn Tractor. In my book, that is as good as it gets for a 30 weight oil - bar none. Higher flash point than Amsoil Marine 10W30 (238C vs 230C). Lower NOACK to boot, than Amsoil Marine (5.4 vs 7.8). Probably better than Amsoil small engine oil that everyone else uses, if you want to nit pick.
Guess you could say it was Overkill + Overkill = Insanity. If I had more of it, I would do it again. I am guilty, so Convict me. In my case, it was only a 2 quart oil capacity. However, it worked like a charm, and the oil level did not drop an ounce, all summer, from where it started.