Just an update on the question of whether to mount the ELT internally. I just finished putting the Poly-spray on with a nice clean finish. I took an ohm-meter and probed in with the two leads about 6" apart. I still had "infinite" impedance. This implies the coating is non-conductive and will cause no loss to the transmission of the ELT signal.
My earlier post where I said that the poly-spray rep said that it is like a sheet of aluminum - I question his statement.
Tom