Ok. But.... that's exactly what I've done.
1) Standard Joomla article. (text, readmore, text with image)
2) Selected options in NSP to create/display thumb of first article image (full article)
3) No thumb
IF.... however, I put the image in the area of the article BEFORE the readmore (the intro), it DOES create/display the thumb correctly
Herein lies our problem.
But anyway, I've coded my own solution as the client could not wait.