Often, when I was singing on the River, I'd be playing for more of the "outside " deck people than ones in the room with me----that via a very poor speaker system. I needed something to keep me sounding acoustic (a Martin D-76) and make the most of a bad situation.
I used a strip of some material or other that stuck to the top of the guitar with double-backed tape. It picked up the sound right from the wood and produced the most natural sound I've ever heard on an amplified Martin.
Just a suggestion.