The pilot was receiving instruction in a tundra tire equipped tailwheel airplane. He stated that this was his first time operating an airplane equipped with heel brakes. Although not proficient, the pilot did possess a tailwheel endorsement. He reported that on taxi he had difficulty reaching the heel brake pedals, and had to physically remove his feet from the rudder pedals in order to apply the brakes. While landing at an off-airport site, during the landing roll the airplane veered slightly to the left and the airplane nosed over sustaining substantial damage to the vertical stabilizer, rudder and left lift strut. The pilot reported that during the landing roll he did not apply the brakes. During his initial call to the National Transportation Safety Board the flight instructor reported that there were no preaccident mechanical anomalies with the airplane that would have precluded normal operation. Due to the pilots inexperience with heel brake tailwheel-equipped airplanes and his difficulty applying the brakes, it is likely that the pilot inadvertently applied to much brake pressure as the airplane neared the end of the landing roll and subsequently nosed over.