ORIGINAL: BFoote
Close enough for a regular airplane. Its a bit more complicated for a T tail when it is out of the propeller wash. In this case reynolds number comes into the picture and CL of said horizontal stabilizer in such configuration. Then one needs weight of model, dynamic safety factor(inertia of model) one wishes to add. Neutral point... yada yada.
Honest, the results you get from the online apps, T tail or not, are absolutely safe and reliable for a CG range to setup for your first flights on a new airplane. Having spent a couple of years playing with my own design 2m glider that started out with a T tail and wound up with a 'mid tail', and doing the basic formula by hand (the pc's around then were Commodore 64s and such), that basic formula proved to be magic. Mystical, magic, marvelous.... And the reynolds for the tail of 2m is right down there where reynolds gets it's knickers in a twist.
From personal observation, modelers really will be more than adequately served with the answers they get just using chords, spans, sweeps, and tail 'moment', even for T tails. If I remember correctly, adding in any of the fancy stuff merely narrowed the CG range. And any shifts were less significant than the affect on the range width.
Funny thing is how often I've maidened guys airplanes that were out of the range we'd discover after the flying proved they really hadn't balanced the sucker properly.