I love the way you can import a reference pic into Wings***** and instantly switch from orthographic to perspective view. Here I've made the basic boiler shape with a series of extrusions from a basic cylinder primitive. Using SCALE>UNIFORM after the extrusion makes it easy to match the taper of the boiler profile. I can also toggle the visibility of the geometry so I can quickly check details in the diagram. Total time involved for this part was 3 minutes, and that was with a phonecall interuption. *****I know you can import a reference pic as a 2D pic in Bryce, but having Wing's modeling commands assigned to "hot keys" makes modeling against a background diagram a doddle.