It's pretty interesting.....I've seen that 40% scale airplanes weight around 40-50 lbs....When their full scale couterparts weights something like 800lbs....(Edge 540)....The scale refers only to the dimensions then, not to the weight. 40% of 800lbs is something around 350lbs....(!!!) It would be interesting to see a full-scale Edge 540 weighting just a little over 100lbs....
I guess that this achievement (light-weight and high power) is largely due to the light and yet powerful engines available today....From analysing the 3W engine series, it's produces around 1HP for every 10cc...So a 3W100B2i (100cc) produces 10HP....I have here an old (I mean really old, something like 40 years) engine with 250cc, weights 17 or 18 kg and produces 9HP that my father used in his homemade car.......Definetely not flyable with this weight....

As I said earlier it would be interesting to see a full-scale airplane with a weight a little over 100lbs.....But would it be possible applying the same structural design of 40 and 50% airplanes?????