That airplane, made out of hardwood, is going to be (1) heavy and (2) tail heavy. It is going to have to have some nose weight to be flyable, and fly fairly fast to stay in the air. Looking at it I agree that the MP3 2.5 cc is a little much. Maybe one of the heavier 1.5 cc diesels. The prop and the width of the cutout for the engine should be good clues. For an 049, I would use balsa and perhaps extend the nose a little.