Thanks as usual Michael, and sorry for putting you to all this work.
Your suggestion that one needs to allign to the grid--for which snappimg to is not (?) required--adds another finness which I had not been aware of.
You have somethng to investigate so I will leave that for the moment.

In respect to that iges file image. The dip in the front should be, as it is, in the front, as with the 3DM file, but the curved up side should be on the right of that---not the left! VERY, VERY wierd!

Don't dispair, what a pleasure to have an app that does not crash!
Brian