SEA86FA174

N3HW, a stits SA6B, was being flown from an airstrip with a density altitude of about 7,800 feet. The plt lost control of the acft during initial climb and the acft descended into the trees, struck the ground, and caught fire. The plt stated that during climbout it felt like the controls weren't responding to his inputs and that they were sluggish even though, during the runup, the controls had responded normally. The plt had about 350 hours of total flight time. The plt had flown into this airport before but never in the stits SA6B. The acft was over the manufacturers maximum allowable gross weight with an aft center of gravity (c.g.). The kit manufacturer states that an aft c.g. will produce sluggish control responses. Trees were present at the end of the airstrip and a slight tailwind was present.