The pilot reported that after takeoff, his passengers were uncomfortable in the "bumpy" conditions, so he returned to the departure airport for landing. He said that due to his passenger load and the crosswind conditions, the owner of the airplane advised over the radio that the pilot should perform the landing with flaps set at 10 degrees. The pilot stated that the airplane "ballooned" on the first touchdown, and that the second touchdown was "harder than normal." A witness stated that there was a direct crosswind, and the airplane touched down with then nose pointed 30 degrees right of centerline. The airplane "porpoised" and landed on the nosewheel first a number of times in succession. Inspection of the airplane after taxi and parking revealed cracking and buckling of the wings, fuselage, and engine firewall. The pilot reported, and inspection by FAA inspectors revealed, no mechanical deficiencies that would have precluded normal operation.