I think what Bert was saying was that a little lift
on the glide, and your 20 will match a 20B. Or a little
sink on the run, and your 20B will fall behind a 20.

I would start off with the stock 20 polar, or maybe
shift it better by 2 or 3 MPH for the same sink rates.
Fly this, and see how your plane does relative to
that polar. Just think how happy you will be if your
glider is better than the polar you enter into your
glide computer (you get home higher than you thought
you could!) and how sad you will be if it is not as
good as the polar (you keep meeting cows and farmers
within 5 miles of your home field).

Remember, the differences between serial numbers of
the same model can be far mor than the difference between
models.

Start conservative, and work up to what it really can
do.

My nickel's worth.

Steve Leonard