I wish some of the experts would chime in, at least to give me confidense, I am not giving out bum info. For me, a relative newbie, I keep the handle blocky until I get close to a finished tiller or close to 26". I won't layout the handle or sight window until then.
But I simply account for 2" of fade on each side, 4" of handle, and 2" of sight window. That will make the center of the handle 4" from the bottom limb, and 6" from the top limb, but most of the pressure of the way I hold a bow will be 1" above the handle center.