Thank you very much for your thoughts on this!
*
The hull is solid, so there is no "core" issue.**The unit I had in mind is the Airmar M260
http://www.airmartechnology.com/uplo...hures/M260.pdf* which is filled with propylene glycol to address the other interface issues you raised.
*
So with all this in mind, one of the other comments was to have redundancy, with which I agree.* My original*concept was to have one "through-hull" and one "shoot-through".* So now I question - do I get two Airmars?