You're not seeing the whole structure because its not made yet but its not suspended, its going to be cradled between that middle beam and the lower beam with three brackets. I know its not going to ride like some 80's aluminum road bike but according to my my computer models its going to have a torsional rigidity of 3.7 Newton meters per square inch (JK).That crank turned out well. I wonder how stiff that will be with the BB suspended below the frame in the cradle brackets. Although the brackets are aluminum, and they look fairly thick, so probably nearly as strong as a thin walled double butted chromoly frame would be.
Head tube looks like a nice fit. Adhesion for the connection to the frame?