If your going to really 3d get the best airframe possible. Considering your insane altitude you need a much higher power to weight ratio than most need at sea level. But to 3d well you also need a light wing loading. Generally those don't go together so you need to start with a nice light airframe. A profile will fit the bill. I suggest a swany(swanyshouse.com) mojo or omp plane. A saito 82 may be acceptable for 3d without sacrifice weight or power. Defiantly get a second opinion though. Welcome to 3d.