If you don't mind a little extra work, here's what I did, that many others have as well, and worked perfectly. Put your new turbo on. Drive the car for a week to put a 'carbon track' on the exhaust housing. Take the turbo off, the exhaust housing off the turbo and bring it to a machine shop. They'll use a milling machine to center your enlarged hole on the carbon track, rather than the existing hole. This way you can be certain that the enlarged hole will be in exactly the right place for your turbo-THDP combo. This is one of the many 'little things' that add up to better performance from your car. FWIW, I had my WG hole enlarged to 1.125" [1 1/8"] as the THDP puck is 1.350" this leaves a full circumference 1/8" to seal, when you only need 1/32" sealing surface according to Harry at PTE.
Good Luck,
Jim