I am almost finish building a dust collection system to go with my paper model grain elevator. The prototype that I am trying to model is the Alberta Wheat Pool elevator in Leduc, Alberta, Canada. The intake duct took longer than expected to design and build in paper because of the transition (reducer) between the rectangular duct and circular stove pipes. The transition (reducer) looked fine in Sketchup, but very difficult to fold into the correct shape due to its small size and my large fingers. My work around was to make one end of the reducer an integral part of the rectangular duct and therefore I only had to shape the other end to match the circular stove pipe. Meanwhile, the legs for the dust collection bin turned out stronger than expected, thanks to heavy cardboard (heavier than 100 lb or 199 g/m cardstock). Because the roof of my receiving shed is lower than that in Leduc, I still have to design additional elbows and pipes to reach. Hopefully in a day or two.