Define penetration.

whbush wrote:
So you can't penetrate downwind? So going down wind is withdrawing?

Downwind I'd be much happier with a real good floater than a
jumbo jet (or other sinker). If you look at the data with
the 30 knot tailwind, a PW-5 has a better L/D (54:1) than a
Salto 13.6 (53:1) even though the best still air L/D for the
PW-5 is 33:1 vs. salto 35:1.

For the most part it doesn't seem to apply too much, because
the minimum sink rate for a lot of modern gliders is very
similar (a glider with a 2-3 knot minimum sink
doesn't sell well).

Of course none of this has anything to do with airspeed at
minimum sink, which is for thermalling and is another matter entirely...
This speed seems to have quite a variance in modern gliders...