The pilot stated that he was performing maintenance on his airplane and running the engine at full throttle to verify the exhaust gas temperature was within limits. He said that after the last adjustment and anticipating another adjustment, he only latched the canopy enough to keep it in place while performing a test run on the ground. After the test run was performed, the pilot departed without properly securing the canopy. Shortly after takeoff, the canopy was “ripped off” the airplane and while returning to the runway, the approach was too low and the airplane contacted trees on short final. The airplane landed short of the runway and did “two pancakes” resulting in substantial damaged to the fuselage, and firewall. The pilot further stated there were no mechanical failures with the airplane that would have precluded normal operation prior to the accident.