Arthur --

Yes, PinPoint's usage of SExtractor is transparent. All you have to do is set Plate.UseSExtractor to True and adjust Plate.SigmaAboveMean accordingly. See the PinPoint reference for scripting info. There is a LOT there, including a large set of mapped properties that correcpond to FITS fields. You should not directly write to FITS when there is a PinPoint mapped property available.