You did nothing wrong. You do, however, have to go back to the aircraft editing page and lengthen the landing gear. Try different values for the main and nose or tail wheels until you get a look you like. It seems as though G2 does not properly position the plane in relationship to the ground when the aircraft is enlarged. You then have to adjust its position relative to the ground by making the gear legs longer.

Also, try to maintain the relationship between the main and the nose gear. Otherwise the plane will sit at a different angle or even fall back on its tail if it has nose gear. Hope this helps.

Steve