I saw that picture and the first thing I thought of was why would they put the exhaust pipe right over the pilots head. The noise would be terrible ! Over to you !
Out of curiousity, what is the pounded metal work around the engine bay called ? I have also seen it on the Spirit of St. Louis.
Just a guess...the cowling around the engine compartment probably could be made stiffer by creating the pattern of imprints in the metal....otherwise it might flutter in the slipstream (on the other hand, there's probably a drag penalty for the pattern too)
Not neccessarilly, you use imprints on golf balls to improve their caractheristics while flying through the air. It actually reduces drag.