The CC100 was attempted on several double basses, mainly using the dedicated double bass clip. Several trials were performed, trying to establish the optimal distance & location of the microphone.
The quality of sound is fair, but not quite at the level of an LDC mic. The main problem is the relatively low sensitivity & output level, resulting in relatively poor S/N. This is because the double bass is a relatively quiet instrument (compared to, for instance a trumpet or a snare drum).
Qualitatively the best results are obtained with the microphone placed close to the top, with the goose neck sticking through the bridge feet. However, in this close position it is quite a focussed point-measurement (though not as focussed as common DB PU's, as the Realist or contact mic's). Moving it farther out results in a more global perception of the instrument, yet at the cost of poorer S/N.
f-Holes need to be avoided: the sound will be strongly tainted by the Helmholtz blow resonance resulting in a dark grotty wash.
Sound quality can be further improved by setting judicious (sharp) notches on your pre-amp, after spectral analysis of the raw data.