Tonight I fabricated a simple drain tube for the upper AOA port. It's intended to channel the drained water down and out of the wing, as well as helping to guide the pin to the drain plunger. I started with a VA-112 fuel tank drain flange, which is normally mounted on the exterior of the fuel tank skin. I drilled another set of mounting holes and countersunk them so I could mount it the other way around:
Here's the drain hole and the rivet pattern. These rivets will be flush, fulfilling my goal of having none of this stuff poking out in the breeze.
And here's a shot of the finished product. A piece of clear vinyl tubing from the aviation aisle at Lowe's is slipped over the drain, and feeds down to an AN816-6-2D pipe nipple that I had lying around. That's kind of an odd size for normal use, but it worked great for this application. The tubing is a tight enough fit on both ends that I didn't bother with hose clamps.
The angle between the two ends is a little funny because I didn't plan to do this whole thing originally – I just located the hole where it was a straight shot up to the drain plunger, which makes sense if you're just going to use the drain pin without a guide tube. The bend in the tubing is due to the fact that the upper and lower skins aren't parallel here, which I'll allow for next time. I'm pretty happy with how this first attempt turned out, though.
This was probably overkill from the point of view of draining out water – I'm given to understand that hardly any water ever enters the AOA port in the first place – but it does a dynamite job of guiding the pin to the plunger when you're poking it up into the wing without being able to see what you're doing.