Mounting Rapid-Air chuck mount on tin

[SNOW JW]

Installed all of our rapid air system on our sheet rock with backers & it turned out great. I now have 2 of the aluminum blocks to install on the steel siding on the outside I have installed wood backing but does anyone have any pictures or ideas for the rough tin?

Thanks

 

[CNGsaves]

Somewhere on GJ is example where guy had also used contoured "PVC wood" backer on outer tin as well. Thus, the tin wall was sandwiched between outer "PVC wood" and inner wood backer. He just shaped the "PVC wood" for outside piece so it conformed to the tin, resulting in flat mounting surface. Then you can paint that PVC wood same color of tin so it will blend in, yet never rot.

 

[SNOW JW]

Anyone have pics? I did a search but can't find it.