I have a 50 gallon poly water tank that we had to vacate when a bow thruster installed. The tank had to modified for the thruster installation They have attempted to weld the tank a couple of times unsuccessfully. I would like to install a bladder in the tank. how does the plumbing connect? Can the bladder be custom sized to fit? I thought I could just cut the top off the tank and the bladder would sit inside the existing tank? Doable? recommended vendors? The existing tank is rectangular....