Thanks for the answer, Bill.
Just wanted to clarify one point -- how does the distance between the front of the lens and the port glass if you put a 45mm macro lens inside the longer 60 port decrease magnification? I was under the impression that for maximum magnification with the 45mm, the subject would still have to be a few inches in front of the lens (in other words, likely still in front of the port, not inside it. So the magnification should be the same if you can get the subject right against the port?
Or is there some air-water interface thing I'm missing?