Cutting a hole in sheet metal

I think the plasma and some circle frames would do the job, finish the rough edges with a rat tail file and make sure its sanded smooth. I just bought a handful of 1/4 inch woodruff keys and they are wide enough to make a 2 degree (1.7) offset bushing: file a step on the right bottom and top left. That will advance the cam to the crank enough to negate the shorter cam to crank distance without needing a head shim. Standard compression is gonna take a little bump but it is what it is. Non interference motor.