With no adjustability, I would say the chances of hitting on an acceptable
balance level will be slim to none.

There could be feedback problems with the inputs backfeeding from one to the
other, possibly.


I've plugged one of the cables into the intercom system and I can
adjust volume going into that with the intercom panel and cut out the
cabin speaker to prevent an echo. The second microphone can go to a
poition where the engine noise is best, a little experimentation and
I'm there, I'm going to work on it tomorrow.

PS. Vibration was a non-issue due to the amazingly smooth flat-4 engine
up front; or maybe it's the stabilizer in the Camera? Either way...
it's ok.