Building a Tower?

So I am thinking about building a tower for the 2001 nautique I am about to buy. I really like the design of the joystick universal so I am going to copy that shape. My friend has built 8 towers before and he is willing to help me out. My only question is will 1.5 inch aluminum tubing be strong enough? The joystick universal uses 2.5 inch aluminum tubing. The reason I ask is because I found a place that sells adjustable flanges for 1.5 inch tubing.