Corrugated metal siding: Should we install a backer for electrical & pipe penetrations? – GreenBuildingAdvisor

We are installing vertically hung metal siding over Coravent rainscreen. Two questions:

1. What is the best way to finish around pipes that penetrate the sheathing? We already have the pipes themselves flashed with a peal and stick gaskets from Building 475 but do we need to build a backer block with a hole cut out of it, slip the pipe through, flash the block and then side around it? Current plan was to cut a 10×10” flat piece of metal screwed to sheathing, flash the sides and top with zip tape, and then side around it. I’m unsure how this would work with the Coravent though since the j-channels and trim sit over top the Coravent everywhere else to keep the air gap behind. 

and second question… 

2. What is the best way to flash or finish the areas where exterior door lights will be hung as well as the door bells? Originally we had planned to drill a small hole in the siding, pull the electrical wire through and mount these on top of the siding since the wires to sheathing were already flashed using gaskets from Building 475 and the siding sits over Coravent rainscreen. Would this be acceptable or do we need to build a backer block, flash around it and trim the siding around it? I have attached a photo (While it’s not the same siding direction or same lighting, kind of shows how we were thinking to install)