Bud,
Great idea about using the coming for a speaker enclosure. They would have  
to be big enough to put out a good sound and the mounting would really have to  
be well done to eliminate any speaker vibrations that would detract from the  
overall sound quality. 
I mounted mine where I thought they would fill the boat with sound and  still 
not interfere with sailing. Yes, I really do sail from time to time.
 
Rummy