Took everything apart today so I could weight the various pieces on my 3# electronic postal scale. Aileron servo weights are taken from HiTec specs, as I don't have them yet.
Airplane (land) with pack: 4# (64.7oz) W/L: 18.8 oz/sq foot
Airplane (sea) and pack: 5# (80.8oz) W/L: 23.5 oz/sq foot
Weight added by float conversion: 16.1 oz (1#)
As I'll have at least 6# of thrust, even with the floats on this critter will honk. 700W for 5 pounds works out to 140W per pound, and in the land configuration, 4#, it's 175.
I can't wait.