There is really no benefit to opening the hole any larger on the stock turbo. This is to help reduce boost creep on larger turbos and high boost. Enlarging the hole with a stocker may cause more problems than it solves. If you really need to blend on something, with the elbow off, radius the INSIDE corners of the wastegate hole (leave the outside corners sharp) in the exhaust housing, but do not open the hole diameter. The only result of opening the hole diameter is you will have to shorten your wastegate rod to get your boost back to where it is now.
If you open the hole and bolt the elbow on with no other changes, your car will SLOW DOWN. Guaranteed.
If you bought an elbow with a larger puck, you are all all set when you buy a turbo with a larger wastegate hole.