Also from the ground effect page:

  Wingtip vortices are a major cause of induced drag,
  which refers to any drag created as a side effect of
  generating lift.

Less drag -> more efficiency -> less power required to maintain altitude. I don't know how much of a factor this would be compared to the cushion, though, so we'll just have to wait and see. Given that he's already bought and engine and molded a nice, shiny shell, my guess is that he has plenty of power.