He's done thousands of these, so he's not going to be thrown by something as minor as needing to take a little extra off.

I know for a fact (both women were there with me) that he operated successfully on a woman with a penis that was under 1" erect and a woman who was only about five feet tall. I have heard other stories about people who have substantially atypical anatomy and went to him, and it was fine. Incidentally, it didn't occur to me to mention this, but he prefers to give everyone around 5.5"-6" of depth and use the remaining skin for the vulva, so it stands to reason that he must have to "trim" quite often.
I bought disposable douches from Target, so I don't really know much about the alternatives, but the orange dilator is about an inch and a half in circumference. (My thumb is maybe 1/5 the size!) I would assume that if you can fit the dilators, you can handle that applicator - and if you couldn't fit the dilators, you would have other issues. I would, of course, go by whatever he recommends, but I assume the instructions weren't very clear or you wouldn't have to ask...