Foam Board used between shingles and new metal roof.

I am considering a metal roof to replace my shingle roof. A contractor has recommended placing one inch rigid foam board (with a aluminum film covering) over the old shingles and placing the new metal roof on the foam board and screwing through the metal, foam, old shingle in to the OSB deck.

I can see this providing a smoother surface for the metal to lay on plus added insulation.

Is this type of installation an acceptable method?

Everything defaults back to the panel manufacture and what they require with regards to attachment and decking.

Does it work...yes.

Is it preferable to remove the shingles in my opinion...also yes.

Thank you, will check with the metal mfg. to see what they recommend for their product.