We get this question a lot and we are currently working written instructions for installing lighting/fans/porch swings, etc. into our UpSide Deck Ceiling. Because there are so many different configurations there is no single correct answer. We recommend following the installation instructions of the individual products and remind people that the Upside Deck Ceiling System is not designed to support the weight of ceiling fan, large lighting fixtures, swings and other add-ons. These things need to be attached directly to the deck joists and/or supported using the proper mounting hardware.
We don't have written instructions regarding electrical box install, but here are some guidelines:
Please use an outdoor-rated electrical box and follow all local building codes
The channels are 6" wide, so try to plan ahead to mount the fixture in the center of a channel. (Keep in mind we start/stop on partial channels for the deck ceiling install)
You will need to cut a hole in the channel where the fixture is. Please only cut the hole just big enough to fit over the fixture. The closer, the better.
Please do not cut at the seam where channels join together, you will definitely have leaking if you do so.
Once you have the fixture and the channel mounted around the fixture, you will need to use an outdoor rated sealant/caulk to seal around the fixture. This will prevent water from coming down into the electrical fixture.