Hi Chris,
by chance on my way back from the chiropodist this afternoon i noticed a similar corrugated clad building over a hedge and I noticed that it had a shallow pitched roof off of either side, starting about two to three feet before where the gutter would be and going off either side with the gutter probably in line with where the gutter would have been at the end of the curved section. This would make things easy for you as there would be no need for anything to be 'under the roof' as it were.
regards
Mike