Minimal area is correct.
The smaller the area of the PSF the better the separation from other stars and the better the statistics. The PSF above is what comes out of Star in the star list. They arre comparable. I have had great difficulty getting the I filtered PSFs to be smaller than 7x7 though I usually can get V to 5x5 at the same time. I don't seem to be seeing as much disparity in focal length between the two as you are getting.