This is an intriguing idea. I've been interested in AOA since my university days in the 1970s. I flew my LS-3 for over a decade using a small bubble level to set the continuous flap setting of that glider (not perfect but not bad). And I had the side strings on my ASW 24 canopy for about the same amount of time (helpful at times but susceptible to gusts and slight slips/skids, as you said).

I'd be more interested in the kit than the finished instrument.

One concern: any port on the underside of the fuselage is subject to clogging when landing in dirt fields. It's not likely given the angles that you're talking about but I'd have to add one more item to my pre-flight checklist. Oh, well.

How robust are the pressure sensors? I assume if the electronics are not switched on that there is no danger of damaging them even if some idiot blows into a probe or port.

Chip Bearden
JB