Originally Posted by
continentalclub
Quite simply, the rectangularly-footprinted Club World seat pods will not fit in the tapered nose cabin of the 744, whilst the F seats are specifically designed to do so.
Additionally, the floor is more substantial (and therefore less prone to flexing and the attendant disturbance to pax) on the lower deck and there is no through-traffic to the cockpit.
One also has to think of accessibility issues. If all of F (or all of WT+, for that matter... silly, I know but VS does something similar) were on the UD, somebody who is unable to go up or down stairs would not be able to book a F ticket.