I have the Decathlon and it is great fun to fly! There is a certain amount of strength with balsa planes but there is also alot of work to get them flying and keeping them flying if you are rough with your landings, I would probably suggest you go the Cessna or even a T28 to practice your take offs and landings more. Once you can nail 10 or 15 landings in a row, then move up to the balsa, it will save you in the long run. The reason why there is such a discrepancy in weights is because items like planes are shipped on their lineal weight as well, it is a long box and thats where the extra shipping goes to. The box may not be close to 4kg but it is longer than standard and that is where the delivery company stings you.