The second thing; slower rate of timing advance until higher rpm.
I find that a back cut intake increases flow, on the bench anyways. And breaking the outer edge of the exhaust valve also helps, since flow is "reversed". In a perfect world, I'd turn a radius edge on a lathe. Think of how air wants to flow, then take steps accordingly. There are other factors in consideration also, you don't want sharp edges, particularly on exhaust valves, for example.
This isn't large gains, but if you have the time and resources, it generally doesn't cost much $. In rules restricted stuff, you scrabble for every little bit. S/F....Ken M
