Put it on the top of the tank. What if, God forbid, you ever had to open it when the level of tank were above the bottom of a hole in the side of it?
However, it's no longer necessary to gain access to the inside of a tank to install new fittings...thanks to a li'l doodad called the Uniseal http://www.aussieglobe.com/uniseal1.htm
(Scroll through ALL the pages to see how it works and the price list). It WILL NOT LEAK! Email me and I'll walk you through how to use it to install new hose connections.