"Just curious if you tried using just one mic of that B-C2 pair. And if you did, how did that sound? Or.... was the overall quality of the c2 just not up to snuff?"
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Yes, in various locations. And, as I said earlier;
“I don't think they are terrible, . . . It's just that I get a much better sound from any of the others listed above.”
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I also did several/many dual mic configurations with them. Mostly to 2 separate tracks for panning/mixing options. I just did't like the sound of them on acoustic guitar compared to some of the dedicated vocal mics in my collection.
For a 2 mic recording I can now use the AKG P170, which sounds great, and the Behringer B-2 Pro (large diaphragm), or any others I have and feel like I'll get a much better sound in the end. A few days ago I recorded several passes of the 12th fret, 15th fret and the lower shoulder area with the P170 and the piezo/preamp to 2 separate tracks and get a very nice sound that way. The guitar is a Yamaha FSX830C with the ART preamp system. It actually sounds really good live where I take advantage of tapping/thumping on the soundboard a bit for getting the piezo to put out some of that tappingthumping to the PA system at times. But, recording using the onboard preamp I roll off all the lows, mids at a specified Q/sweep, and leave the highs flat. So, I'm only/mostly recording the thin sparkle of the piezo and blending that in with the mic recording.

Does the noise in your head bother me ?