Accurately measuring system bass response is certainly challenging, in my experience. For the most part, I've just ignored it. Some of my stumbling attempts at near-field appear earlier in this thread.
I think I'm gonna punt and try in-box per Small, but I still can't get Andre interested in selling me a second CLIO mic to do it with. He just won't respond to my phone calls or eMails.
Ground-plane also looks interesting; gotta read up more on that.
For now, it's near-field and its shortcomings, though I'm getting better results with it lately....