Pushed to its limits, the 18-gram balsa wood structure, designed and built by students from Hillcrest High School in Dallas, finally buckled with a bang under 220 pounds of steel plates. This test involving structural design was one of the many competitions held Saturday at Temple High School as part of the Texas Odyssey of the Mind North/Central Regional Competition. Gray Garmon, a member of the Hillcrest team, was not surprised by the structure