On first impression many people ask "Is it aluminum?" because BRUNI's tubes are fat. When I say it's steel, the only proper tandem material, "Is it heavy?" comes next. "Pick it up." and "Wow!" follow. My frame is laterally very rigid but weighs less than 10 lbs. and builds up to a 30 - 38 lb. bike based on component choices. While less is better when it comes to weight on bikes, my original objective was comfort; lightness is icing on the cake. Lateral stiffness and vertical flex are the elusive goal of tandem builders everywhere, but usually we settle for a compromise, often a rough bike with a bounce post for survival. This because most tandems are triangles, non-compressible geometric forms, when viewed from the side, but a thin line viewed from the top. This 2D profile produces exactly the opposite: stiff vertically, soft laterally. The picture below illustrates how to bolster the 3rd dimension. The available between leg space is a thin triangle with a 6" width at its base at the pedals. I have used top tubes as large as 2" (8 x stiffer than a "classic" tandem) by sizing my stand-over somewhat lower than classic--more like a mountain bike's. This allows easier mounting also. I build my frames "open"--no triangles which, along with low or curved seat stays, achieves the second objective of vertical flex.