I was against using the blue stain, but it turned out pretty cool. We still need to add some crossbars up top, but otherwise it is done. Here's some pics of the construction and the result.
Most of the compound angle calculators on the internet are pretty terrible at describing which angle is which and where they're measured from. I ended up just calculating them myself. We ended up ignoring the Secondary angle; it was something around 80° for the steepest sections, not a signification deviation from 90° over the 1/2" thickness of the louvers. Plus it can't hurt to let them breath a bit, I suspect we'll have problems with some of the more enclosed bits rotting within a few years. Here's a diagram showing the relevant angles in this situation and how to calculate the Primary and Secondary angles that need to be cut in order for the louver to sit flush with the fence.