MIMF

The general method for adding a side soundport is to reduce the size of the main soundhole to bring the air resonances of the box back to what they would be normally.
That being said, there is no formula for how much to adjust the soundhole sizes.
Alan needs to come in here with a long post on all the particulars.
Bottom line is that Jason's suggestion of a sliding door on the port is an excellent one. That way it can be adjusted to get rid of the wolf.

Adding a decorative "rose" to the inside of the port may allow you to reduce the size of it while avoiding any extra refinish work.

Thats twice you've dragged me out of a protracted lurk with a stunning instrument - bravo!

I think you want to have the total area of the port and the sound hole add up to the area of the sound hole of a guitar without a port. With the size of your port, that would be difficult to do and still have access through the soundhole. I agree, the sliding door on the port sounds like a great solution in that it could be adjusted to what ends up sounding the best to him.

If I remember correctly from some of Al's old posts, it is not as simple as making the area of the port and soundhole the same as the normal soundhole. The position of the port relative to the soundhole also makes a difference. I think he said the farther away and/or the bigger the port the more effect (of whatever it is going to do) will be. I seem to remember him saying that the ports can be pretty darned small and still provide a good monitor for the player (decreasing the overall effect on the tone).

I could have all this wrong since I am going from memory and often don't fully understand what Al is saying in his wonderful and informative posts.

AC can, of course answer for himself, but my takeaway from his extensive soundport testing was that only a very small soundport was useful for giving the player a sense of the sound "out front". Any larger was detrimental to tone. He also seemed to imply that a small soundport has such little impact on the guitars resonances that offset in the sound hole was unnecessary.
Given that, I think the idea of putting something decorative in the hole to reduce it significantly sounds like the best suggestion so far.