Personally i would not use a latex caulking on fiber cement.
Attaching hose bib to metal siding.
This video shows a unique and ez way to mark and cut out an electrical box hole in metal siding.
Twist the connector on the reel s short hose to the hose bib and fasten the end of the garden hose to.
The hole saw will likely be dull by the time you are done drilling.
It slips into the groove between adjoining slats and once it clicks into place you can hang items as heavy as 12 pounds.
My main tool for perfection.
Press your bit into the siding that covers the outside of the house just far enough that it makes a hole with the centering part of the paddle bit.
Clean the dust off the siding caulk around the perimeter of the hole then slide your hose bib in and use two 2 stainless steel screws to hold it on.
From the outside slip on the plastic gasket and push the hose bib through the hole.
Then go outside and complete the hole by drilling through the siding.
Predrill a pilot hole for the screws with an 1 8 masonry bit.
The easiest and safest way to hang something from vinyl siding is to use a siding hook.