The pilot of the experimental, amateur-built motor glider was landing on a 1,926-ft-long, 24-ft-wide runway with about a 6 knot quartering tailwind. During his first attempted landing the motor glider was high and fast on approach and the pilot elected to go-around. During his second attempt, the motor glider was also high and fast but the pilot elected to continue the approach to landing, using full air brakes and wing flaps. During the approach, he slowed the motor glider to 40 knots (6 knots above stall speed), and the motor glider then seemed to drop from about 10 ft above the runway and land hard. The right landing gear leg collapsed, and the motor glider veered off the right side of the runway, struck a vertical approach slope indicator, and was substantially damaged. Review of the Pilot's Operating Handbook revealed that the final approach speed should always be 55 knots with full flaps regardless of approaching with zero or full airbrakes. The pilot reported that there were no preimpact mechanical malfunctions or failures with the motor glider that would have precluded normal operation.