Replace outdoor fixture where existing fixture larger than new one
A tricky situation. If you can't get a piece of texture matching siding that you can paint to match, then I'd go with Aluminum flashing that you can easily paint &amp; profile to the siding. You'll want to caulk &amp; then screw or pop rivet the siding or flashing chunk to just under the siding's closest above rib to act as a roof for your patch, you're screwing the patch into just the siding &amp; not the building or sheathing. First though, screw in an oval piece of plywood to the building's sheathing to fit in the old hole &amp; fill-up the recess to mount your patch &amp; new fixture to, center drilled-out for wiring. Use aluminum screws or rivets to avoid rusting, caulk your patch to the siding &amp; caulk your fixture to your patch. Also, screw plugs with plumbing tape into the new box's unused holes, even if it's a bottom one.