Vented roof over

[vintage steel]

Okay so I just spent a pile of money for enough steel roofing to cover my Double wide. I was going to do a pole building, but time constraints, weather turning cold and (of course) cost, have limited me to a roof over.
I have seen rigid foam board nailed between strips of lath and the roof screwed to the lath.
I was considering:
Nailing the foam board directly to the roof with no gaps.
installing lath over the top of the foam board allowing air to pass from the soffit under the tin, to the ridge cap. I think this would create some sort of ventilation between the foam and the roof, limiting condensation... I think.

Any problems with this system? I have seen it on houses, but couldn't find anyone who has done it on a mobile.
What do you think.

[Greg]

The problem that I could see right off may be the foam allowing the new roof system to compress, If the new roof compresses too much you will have leaks around the screws.

Greg

[JD]

You will need the wood to receive the screws and make a solid connection between the steel and the framing.