I believe the correct answer is "... depends."
There are cantilevers and then there are cantilevers.
As John originally drew the little house plans, 14 foot wide on 4x8 beams, he set the spacing of the beams to have 2'2" overhang measured from the center of the 4x8 beam. That's with 2x6 joists on 16" centers.
I have some snow load to deal with too but not as much as in the Chama area. I feel pretty comfy with my specs... 2x10 joists on 16" centers, total length 15'9", and 12" of overhang, no loft.
This one of those calculations for which there are no easy tables; at least I don't have them. An engineer would do load calcs for common materials, modulus of elesticity or something, etc. Then multipy that by his safety factor, etc.