THE PILOT/OPERATOR STATED THAT HE WAS ON A FLIGHT TO TRANSPORT A PARTY OF TWO TO HUNT SHEEP. THE DESTINATION WAS A HIGH ALTITUDE, ROUGH STRIP AT A REMOTE LOCATION. THE AIRPLANE WAS A PIPER PA-18 EQUIPPED WITH TUNDRA TIRES AND A 3RD SEAT, BUT THE PILOT STATED THAT HE WAS HAULING ONE PASSENGER AT A TIME. THE PILOT STATED THAT WHEN HE LANDED, THE AIRPLANE TOUCHED DOWN HARD AND BOUNCED. HE SAID THAT HE APPLIED BRAKES TOO HARD, AND THE AIRPLANE 'FLIPPED' NEAR THE END OF THE ROLL-OUT. THE AIRPLANE HAD BEEN MODIFIED WITH THE TUNDRA TIRES, 3RD SEAT, AND A 160 HP ENGINE WITH AN INAPPLICABLE STC.