damn that is a heavy lift like u said
that means total aircraft weight will most likely exceed 700 lbs depending upon flight duration
think 50 cc size elec motors move an aircraft of 40 lbs (large wings) cub style
geared down they should be able to operate as I think 60 to 70 lbs as speed should not be an issue
but even with 6 motors u still have a weight issue.
another option would b e helicopter style similar to what nascar toyd with a few years ago that was gasoline powered.