A good condenser in the vicinity of the outlet may be sufficient... although the bottom end on the digg may be a bit overwhelming in that spot so remember to keep it well out of the air turbulance..
The RE-20 ( a dynamic ) might be a good option as well.... a narrower sonic field than a condenser but easier to deal with later.
If you've got time ,, try a second mic around the mouth , about a foot or so distance to get some upper register.Experiment with a different phase.
Low-cut is recommended to preserve detail upwards.Push the bottom end ( if required ) afterwards in the mix.... somehow may be a bit safer. :wink:

A friend of mine is experimenting with this at the moment, mainly for live work.. He is going to try acoustic guitar style contact mics, saxophone or drum clip ons and things like that. It might be a while before he gets results worth reporting though, it is a long term project....
It is an interesting instrument to try and capture, so simple yet so complex...