I think we need to know the exact moment where 1 cuil begins and 0-0.999 cuils end. I propose bringing in the concept of radial categories from linguistics and cognitive science.
For those who are unfamiliar, here's an example: think of a bird. Chances are you came up with something like a songbird: small and feathered with functional wings. This is an ideal bird, and is at the center of the radial category. All the birds that are 'less than ideal,' or one characteristic removed from the ideal bird, come off the center of the category. Penguins, ostriches, hummingbirds and turkeys would all be spokes off of the ideal songbird. These are all birds obviously, but rarely the first to come to mind.
Another example would be a cup. The ideal cup at the center of the category is something with smooth sides and a reasonable height. The spokes can be coffee cups, sippy cups, the stanley cup, or the intangible victory of a championship (we won the cup!).
Where the radial category ends, after the largest leaps of the imagination of course, one cuil begins.
Obviously this can be extremely subjective. Think of age and context dependent radial categories for 'mouse,' 'physics,' 'school,' 'crack,' and 'gay.' It's a start, though.