How high are the rafters- in other words how long is the drop? There is no magic solution here. If you want to spend money they make "power poles" that you will see in stores dropping down to the POS terminals at the checkouts. These handle both power and data. I think in your case EMT conduit is a good choice. I would choose a large enough size to minimize flexing- depending on the rafter height.

-Hal

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