I think that the custom fiberglass aqualift muffler is an excellent solution and when my original muffler goes it will be replaced with fiberglass. I have yet to see a fiberglass muffler  fail and have installed and built quite a few.  I think it is important to note that most epoxies have a  much lower heat tolerance than the Polyesters so keep that in mind in the selection of the resin.  Most of the commercially available fiberglass mufflers are polyester and also use a fire retardent resin that will self extinguish itself.  I am not too sure how critical the fire retardent resins/additives are since the exhaust hose would probably burn off before the muffler could get hot enough to burn so make your own decision .  The heating issue only becomes a concern of corse if there is an extended period where cooling water is lost. 

Best, 

James Alton

SV Sueno

Maramu #220