I would use fuel tubing on the ports under the front of the tank. Put a bolt in the other end of the tubing and clamp. The bottom of the tank can be sealed by making a small plastic disc, cut from a food container (your gasket). Poke 3 holes for the petcock screws. Then cut a thin piece of wood in the same shape with 3 holes to match and bolt the plastic/wood "patch" to the bottom of the petcock opening.
|