Suggestions to Use Sherline Scale

How do you get the tongue coupler on the scale? I'm thinking of having the coupler positioned so it easily can lift off the ball. Then lower it, raise the jack, lay a small length of 2x on the scale, place the scale under the jack shoe and raise it until it lifts off the ball. That puts it a ways to the rear of the coupler and I have no idea how that affects accuracy.

The directions suggest putting the screw on piece into the coupler for most accurate reading, so if you do it that way, what's your procedure?