The pilot was departing from a remote, gravel-covered, 800-foot long off-airport site, in a tailwheel-equipped airplane. The pilot reported that at the time of the accident the airplane had been loaded at, or near the airplane's maximum gross weight limit. He said that shortly after the airplane became airborne, the tailwheel contacted an area of rising terrain causing the airplane to lose airspeed. The airplane subsequently collided with terrain at the departure end of the site, sustaining substantial damage to the fuselage and empennage. The pilot stated that there were no preaccident mechanical anomalies with the airplane that would have precluded normal operation.