./profit-cli -f test.fits -p moffat:fwhm=10:con=10:xcen=50:ycen=50 shows the simulated Moffat profile at the center of the frame. I did not understand that the xcen and ycen were defaulted to 0 each. I would have defaulted them to half image width and height.

Thanks. That probably does make more sense as a default. I will ask Rodrigo Tobar (the person who implemented the command line side) about this.