Well, I did remember to call at the shop, but it's Wednesday here and he seems to be one of the few remaining adherents to the old "half-day Wednesday" rule.
Corrugated metal sheeting is now almost always to a 3"/76mm pitch - some plastic and reinforced cement sheets are to different pitches at times. In the past, pitches from 1 to 5 inches were used - the shorter pitches were used more often on vertical (wall) panels, and the larger pitches on flat/sloping (roof) panels. The 7mm scale sheet could be used for 5" sheeting?
On the Big Island, one will still come across the odd surviving Nissen hut, with its curved sheets..