Well, I'm not great at estimating their length, especially since they move around so fast! Your estimate seems pretty good for your squirrels (which I think are Sciurus vulgaris, or Eurasian red squirrels) which Wikipedia says have a mass of about 250-340 g, are about 19-23 cm without their tail, and which have 15-20 cm tails. Wikipedia also says "The [Eurasian] red squirrel is somewhat smaller than the eastern grey squirrel which has a head-and-body length of 25 to 30 cm (9.5 to 12 in) and weighs between 400 and 800 g (14 oz to 1.8 lb)." So you are absolutely correct, that the Eastern gray squirrels around here are a little larger. And yes, this squirrel is no doubt well fed (since there is plenty of food at my feeder), but that being said, I think it's mostly the camera that makes this squirrel look kind of fat, and that fact that the squirrel is scrunched up in order to perch on the fence. And I agree that the "hand on heart" gesture is quite cute (although it is usually an alert stance).