We chose steel tube for many reasons. It allows us to build the most complex part of the aircraft in factory jigs, with all critical holes and hard points for spars, engine mount, controls and landing in proper place. The aluminum/steel composite construction with integral roll bar offers great pilot protection. It also saves a builder many hours of time. The down side is cost, which we are striving to keep as low as possible! You can also see another compelling opinion on why steel tube fuselages are a good choice HERE