RE: OS 46AX On A Header & Pipe
You are correct, Ernie.
But as far as this engine goes (and any other ABN/ABL engine), grinding the ports in the sleeve would risk severe peeling of the nickel off it...
As I wrote, breaking the continuity of coating; together with the rather weak bond of the nickel to the brass, would make sure peeling starts from there.
Had I owned such an engine, I would not take that risk...