Figs,
Great questions.
First, a good rule of thumb for the coefficient of pressure pitot/AOA probes is that they can handle up to about 6 degrees of sideslip. I find I run out of rudder (generally) before I run out of tone in the RV-4.
Second, there are two tones in the video; they are being generated by systems we built that generate performance AOA and energy cues in addition to progressive stall warning. All of our work is on our website at
http://www.flyonspeed.org (non-profit, volunteer, open source group).
Specifically, yes, the high (right wing) is stalling first--hence the ratcheting behavior in the departure sequence. My Dynon probe is mounted in the RV-4 plan pitot location under the left wing and there is a second, Alpha Systems probe mounted on the left aileron inspection plate as well, so in both cases any stall warning provided by either probe may be "optimistic" in a left slip. We've got a calibrated test boom that we can mount on either wing tip; so getting some comparison spin data is on the list of things to do to test that thesis and quantify it.
Additionally, the quality of the AOA tone performance is going to be affected by sideslip angle. I can't specifically quantify how much, as we haven't completed that testing yet either--but the 6 degree rule of thumb comes from wind tunnel test and correlates with what we've observed so far in flight. So, you are spot on with your "not too slow" game plan
My 2 cents would be to adjust your system to provide 5-7 MPH/KTS of stall warning tone to build a margin and realize the margin is probably less in a left slip. You could test that by flying a cross-controlled stall as I am in the video and noting the difference in time between hearing stall warning and that first nose bob. If you do, keep in mind the rate of back stick application will affect that result. If you pull hard enough, fast enough, you'll "beat" your stall warning system and stall before you hear the warning tone.
FWIW, we learned testing our first generation AOA tone generator that Dynon AOA calibrations vary from airplane to airplane; so your's is unique and the only way to know for sure is to flight test. Also, if you ever re-calibrate, that will reset your baseline and you'll have to re-test. The first test I'd run is to determine the amount of stall warning you have with your tone selection in a normal, straight-ahead stall and go from there.
Also, in the last video you probably noted that the airplane effectively stalled 4 times before I was able to force it into a spin. In other words, in a slip (left turn, left aileron, right rudder) the airplane is highly spin resistant, so even if you ham-fist it into a stall in the base turn, it will give plenty of aerodynamic warning. I.e., RV's slip great.
In a skidding departure the airplane will immediately roll (spin) at the first stall; which is why this is the last thing you'll want to try in an overshooting final turn.
Cheers,
Vac