With the fuselage length I mentioned, you just put the horizontal tail surface all the way back. Make the elevator hinge line even with the end of the fuselage. It's really NOT that critical. Some people make fuselage sizes in relation to wing chord. The full length of the fuselage would have 75% of a wing chord ahead of the leading edge, and 1.5-3 wing chords between the wing trailing edge and the leading edge of the horizontal stabilizer.

I checked out a Super Kaos...a "classic" design. Span and length are nearly equal. Wing leading edge to nose is one chord. Wing trailing edge to rear of fuselage is 2 chords, so the airplane is about 4 chords long (based upon center wing chord, since the wing is tapered).

It's not so much the areas and length relationships, but where the model is balanced and how much control deflection you have. With most models, a balance point of about 30% back from the leading edge of the mean aerodynamic chord, and control deflections of about 20 degrees or so are good starting points.

As far as whether the stabilizer/elevator is at the top of the fuselage, bottom, a T-tail, or cruciform arrangement....again, it's not really critical for an airplane that flys well. It will make a difference if you're trying to get a specific level of performance. Many times, it's placed for the convenience of the builder when you're talking about a 'sport' model.

If you take a plane, such as the Great Planes Big Stik, you can move the horizontal surfaces around...at the top of the fuselage, bottom, middle, and so on...even make the rear of the fuselage a bit taller to move it higher...you really won't get a lot of variance in how it flies. Even if you turn the fuselage over and make it a low wing, and just flip the vertical tail surfaces to the new upper side, you won't get a lot of difference. For a good-flying airplane, these things are just not that critical.

Now, if you're trying to get a specific type of performance, then they do make differences, but usually only in nuances. You'll get greater effects by changing the wing, tail, and engine mounting angles to give you differences in incidence, thrustline, and decalage.

One plan that will enable you to learn a lot is the RCM plan, "Scotch Lass". It's a basic box fuselage with wing on top. It builds VERY fast and takes a .15-size engine. I've build different versions of it, using the same wing and tail surfaces, but built high-wings, low-wings, stock, and so forth. They all flew nicely. I kept the same fuselage length and wing and tail placements. Balanced at the same point. I even had one version with a slightly-longer tail. Kept the same balance point. Flew just fine.

Not to beat a dead horse, but the basic parameters all WORK...they will give you an airplane that flies nicely. If you need a plane for a specific purpose, then the tuning begins.