As already mentioned Richard, a great opportunity presented to you. I haven't looked a the EXIF data on your images, but something puzzles me. If the first 2 exposures were strictly created by the flash, in number 1, I'd expect the front of the roof line to be severely overexposed being closer to the flash; and number 2, the tree in the background on the second exposure appears to have fairly decent exposure, but is considerably further away from the flash. What kind of metering did you use? I've had a lot of luck using spot metering and locking exposure on the subject (plus shooting at anywhere between +0.3 to +1 EV) when shooting against a white/gray overcast sky.