I nice trick for cutting the holes is if you have a ball bearing around, lay the plate down with the gasket that you've cut on top of it. Then place the ball bearing on top of the gasket where the holes are and give them a tap with a hammer.

This will punch out a nice hole for you. Make sure the gasket hasn't moved when doing the next one. Also if you can for next time, weld the ball bearing to a flatened punch. Makes it easier.

John Like a dog on a car ride with my tongue in the wind