Note to anyone watching... the little DIY altitude chamber experiment paid for the time and energy.

We bought three Egg Timer Quarks, one for two adults and one teenager, moderate soldering skills for the adults, and a new experience for the youngin.

We built one Quark - tested, all was right (startup, tones, continuity on LEDs [simulated ematch], and firing of drogue/main charges [again LEDs simulated the output])
Built the next Quark - tested, all was right
The last Quark was assembled, startup was good, good tones, continuity on LEDs, and ready for launch signal. When we did the altitude chamber test, the apogee event did not occur (the LED did not get super bright like the other two tests), however, the main chute event (approx. 500' AGL) did occur.
We're troubleshooting the possibilities (EggTimer customer support has provided rapid responses) and hope for full resolution.

The key to this, I asked the youngin - "Imagine if that was in your rocket, and the drogue chute did not fire"; he immediately realized the value of the simplistic test.

So, proof of concept - at least on a barometric level. We'll have to trip the accelerometers through an actual launch!