replacing sheet metal roof

I have a friend that has a mobile home unit, single wide, 16X80 manufactured in 1996, it had a metal roof system, the pitch was some what low , maybe less then 4/12 pitch, the roofer removed the old sheet metal, then applied 2x4 laterals " purlens" for attaching the new system too, I believe the spacing was 4ft on the laterals? the sheeting was attached with 2" screws with neoprene washers, the installer provided a drip edge which is enough to drip into a gutter system to be installed later. The catch here is; the codes department has reared their nose into this and state that now they need an engineer to look at the roof since most of this work was done without a permit, thing is, the codes department actually has no jurisdiction over manufactured homes, only stick framed homes, so they have no actual documentations to rely on other then third party observations. No strap members that the manufacture installed were altered or reposisitioned, only the old roof sheeting was removed and replaced with new, the newer material is typical roof sheeting and is much lighter in weight per square foot then the other stuff was, in your opinion, besides the building permit issue, did we do something that would compromise the structure? other work included to the home was removal of the sheet metal siding and we went back with 7/16 OSB exterior sheeting nailed at 8" spacing, wrapped with a house wrap product and installed vinyl siding.