Hayes tanks work great for two line setups but do not work for three line setups. In cowled in engines, I like a third line for fueling and defueling the tank. While the Hayes tanks does have a third nipple that can be drilled out for a third line, that only works for fueling since you can not run a fuel line inside the tank to the back/bottom of the tank for defueling. Please do not suggest that I use a fuel valve in the tank/carb line for fueling because I find that that tends to be unreliable in the long run.

Bruce