Thanks. Interesting stuff. Yes indeed in my racing days I was amazed at the difference in downwind angles between a top racer and an average one. There is more than strategy here - one has to be able to safely and efficiently gybe, esp. in strong wind, which only proficient racers can do.
When I was racing (80s), I was downwinding at higher angle than most, indeed to generate overall downwind speed, as you state. I would say downwind was my specialty then, the weakness being the rest

Lately I've been playing with almost 90 degrees in stronger wind, and it's just amazing how I get there in about the same time. Of course, it's much harder work and riskier (risk of missing a gybe), but soooo much more fun.
OK, will keep playing with all this.
> you cannot come out of a gybe at a higher speed than you would have
That would be one difficult rule to monitor.