Might want to run the turbo on the car for a while before doing that, that way you get the nice carbon build-up on the housing (like on your old turbo in the picture). You can use the carbon to give you a clear idea of where the wastegate puck sits, that way you don't make the hole too big. If you were to port it right now, I'm not sure how you'd get a clear idea of where the wastegate puck is at. It's not always centered over the hole. Look at your old turbo, you can see the wastegate hole, but the outline of the puck in the carbon is offset. Unless you have some kind of grease, smear it on the wastegate puck, bolt the turbo to your downpipe, open and close it a few times, and see if it leaves a clear enough mark.