The pilot receiving instruction for his tailwheel endorsement reported that, he and the instructor were performing touch-and-go landings and takeoffs on the asphalt surface runway. The airplane was equipped with toe brakes, and after landing, he added power to abort the landing, and also applied right rudder as the airspeed accelerated to 30 knots. He recalled that he held the right rudder pedal application "too long" and the airplane veered to the right. He corrected the right veer by applying left rudder but overcorrected and the flight instructor came on the controls and applied full deflection of the right rudder. The airplane did not respond to the instructor's right rudder input, and he applied left aileron. The pilot receiving instruction kept his feet on the pedals and inadvertently applied left brake. The airplane was side loaded to the right, and the right wing struck the ground. The instructor held his control inputs to direct the airplane to the right, but the right wing struck the ground a second time prior to exiting the left side of the runway. The airplane's heading was about 60° to the left of the runway heading, and the wheels dug into the dirt on the left side of the runway and the elevator struck the ground, and the right wing struck the ground a third time before the airplane came to rest upright. The airplane sustained substantial damage to the right wing, and the right elevator. Additionally, the pilot receiving instruction was the owner of the airplane, and reported that he, "had installed removable 1 (inch) blocks on the lower portion of the rudder/brake pedals to reduce the required ankle deflection and allow for applying rudder controls with less likelihood of simultaneously applying brake inputs." The pilot reported that there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation.