The difference between the numbers you see and those reported by others might come down to the units for FWHM.
I suspect that the anecdotal figures reported by other imagers are in arcsecs - this would certainly square with my understanding of typical seeing limitations etc
However, if the software doesn't take the focal length of the optical train into account, then its probably reporting FWHM in pixels. If the image scale of your scope and camera combo is say 2.5 arcsecs/pixel, and your software is reporting a FWHM of 1.3, then that is equivalent to a FWHM of 2.5x1.3 = 3.25 arcsecs, which would be consistent with the numbers reported by others.
As a further example, on my last imaging run with the VC200L with humidity close to 100% I was getting FWHM of about 4.0-4.2 however my image scale is ~0.9 arcsecs per pixel, so that gives me a FWHM of 3.6-3.8"
