You're on, John. In identical aircraft, you fly best L/D, and I'll fly
best L/D plus half the headwind. According to a spreadsheet called
Polar.zip that implements Reichmann's Best Speed equations, in an
ASW-19 with a best L/D of 50 knots, the interthermal flying times and
climbing times are as follows:

50 55 60 65 70 knots
5.92 5.38 4.93 4.55 4.23 minutes, interthermal glide
1.53 1.54 1.61 1.72 1.87 minutes, climbing

As you can see, I'll beat you with any headwind at all. Incidentally,
Speed to Fly for this case is 80 knots.

-John


John Cotter wrote:
Looking forward to racing against you guys who fly faster into a
headwind while out on course :-) Any additional distance achieved by
doing that will be given up drifting backwards in the next (longer)
climb. For this reason MacCready speed to fly doesn't account for
headwind only estimated strength of next thermal. Best avg XC speed
will be achieved through answer c.

John