I've never owned one but with a specific focus on infrasonic frequency response down to 5Hz, I suspect the UMIK-1 is iffy. "
Frequency response: 20 Hz - 20kHz +/-1dB with calibration loaded "
You might consider omnidirectional calibration mics from companies like Earthworks, B&K, and DPA. [Much pricier though]. Not that I'm well read on them but they are some of the big names in the field that come to mind.
UPDATE: Keep in mind that just because some people post graphs showing
readings for low, single digit bass on some mics like the UMIK-1, this doesn't prove they are necessarily
accurate values.