On Friday, January 8, 2016 at 5:36:33 AM UTC-8, wrote:
SNIPThe case that would favor it is very strong lift surrounded by strong sink.

There ya go: +10 followed by -10 not that uncommon here. The tradeoff between altitude and speed is mathematically fixed by classical physics: 1st law of thermo which I think everybody believes. It hasn't changed since the 70s (or even the 1770s). Drag of sailplanes has reduced very slightly in 45 years, which affects it very slightly. 90 knots speed reduction (from 140 - 50) is around 700 ft. (minus energy lost due to inefficiency, but plus gain due to 10 knot thermal). Pushover form 50 - 140 is the same, reversed.

No, I would not do that on a day with 2 knot thermals topping at 2500 ft. But I assume we want a Flarm stealth solution that works in all conditions?