Making waste tank for Shantyboat #481

Hope this is not a duplicate post, the first disapeared in cyberspace.
I am building the waste tank for the shantboat and woul like to know
if ply glued on glass with epoxy then flowcoated would be sufficient
to hold the cr*p and any chemicals some one might use. Am I making a
horible error or as I believe saving money and making the tand to suit
the needs of the boat. regards and a prompt answer would really help
me. I have done a search on the messages but was not successful.
Paul McLellan glad to see the ice go and the temperature rise enough
to make epoxy.