I finished my flash testing today using this scene in the hangar. What is comes down to with my set up is that flash exposure lock works as expected, and you need to crank in 2/3 flash exposure compensation for every stop underexposed. All in all I was somewhat disappointed with the performance of the 350D/580 EX combination. I might be missing something, but the results seem a little erratic. I guess proper exposure comes with lots of experience. Thank heaven I could do this stuff with a digital camera rather than film. It would have been a real expensive experiment with film.