I'm hooking up a 300 watt toroidal magnetic transformer located in my garage; it's rated for inside and outside use, I'm using its plug into a GFI circuit, and I'm using 12/2 (12vac) power cable rated for in-ground burial use. I'm planning on drilling an approx 0.5 inch hole and using 1/2 pvc conduit from transformer through the wall and down the exterior side into the ground. The max load that will be placed on this transformer is expected to be about 40 watts, using LEDs, with a max cable run of about 160 feet.

Is there some other requirement that I should be aware of?