How much cubic footage are you willing to sacrifice for it? Mock it up in your van with cardboard. See how much room you have left to live in. Unless you have at least a 2-foot high-top, or you're a very diminutive person, you'll need to sit to shower. (How do you clean your butt that way?) And since van walls slant in, you'll be leaning forward or sideways. And you'll need a way to get to water heated, unless you like cold showers. And some way to get the water up to shower height. And a way to drain the gray water or hold it. And if you're wanting a flush toilet, then there's another whole layer of complication. (Yay, sweage holding tanks!) If you absolutely need a shower and toilet, then I think you're better off getting something that's already had everything figured out, like a Roadtek or Rialta or one of the Class B's.
