Nope.

Those circles are not exactly your sit bones.
(I measure with a measuring tape directly on the bones.)

Try sitting on your hands and feeling the contours of the bones. Get your index fingers on the outsides of those bones, jammed right up to them. Leave your hands on the chair and stand up, have someone measure the distance between your finger tips.

Outside measurements are only about a cm two more than center measurements most of the time.

If we use your 150mm centers and add a couple cm, we get your outside at around 170mm. If we use your 140mm centers and only add 1 cm, we get outside around 150mm. Take a B17 at 175mm, subtract 2 cm for the cantleplate: someone with 155mm outside and LESS won't be likely to hit the cantleplate.

Depending on your imprints, your actual outside measurements could be right on 152 or they could be out there in the 170s. That's why its so important to measure a few ways and a few times.