Polar diagrams and L/D

I sure need help here.

As far as I understand polar diagrams the airspeed axis is for indicated airspeed, not true airspeed. This certainly makes sense.

BUT, I have also come to understand that an estimate of L/D for a given airspeed can be obtained by dividing a given airspeed on the polar curve by the associated sink rate for that point on the curve.

BUT AGAIN, if the airspeed on the polar diagram is IAS wouldn't an L/D derived from a polar diagram be reasonably accurage only at sea level in standard conditions in still air?

If a glider pilot is interested in the distance traveled for a given loss of altitude wouldn't TAS be more useful than IAS - especially at higher altitudes? Of course headwind/tailwind would still be a factor in how much distance the glider can cover for a given altitude loss.

I've likely just bunged up this entire thing.

Jim