I'm not sure what the drawbacks are,,but I don't see other guys using cheap varnish. West Marines cheapest varnish sounds watery in the can compared to the other brands. Maybe $10/qt. isn't much of a savings compared to the cost of the epoxy it's protecting as well as the labor used to put all that wood together. Recently varnished a kayak with z-spar polyurethane clear "varnish" and am very happy with the results.