Mightybus, I'm gonna do a spiral staircase too. I am going to have a shop weld a 3 to 5 foot extension deck off the rear of the bus. Then I'm going to weld a spiral staircase from the deck to the roof. I will take marker lights and place them up the stairs sides so at night they light up. You are creative my friend. Grey water tanks from water heater tanks. WOW!! I like it I do.