Dave, i have always criticised your interleaver designs as being potentially heavy because of the drivelines. The above guestimate, albeit making some wild assumptions about the construction of the drivelines (based on Goodrich Ti coupling photograph), indicates that the drivelines could be a reasonable mass. However, the concerns about operating costs of such a complex drivetrain are still valid. Equally, so are the concerns about machine rotor system width limiting general purpose landing site access.