No offset in either rudder or engine is fairly common these days.  If the leadouts are in the right place and the tip weight is about right, no problem.  Offset engine seems to work better than offset rudder.

Bellcrank location is of little importance, it's entirely the leadout position that makes it work...or not. Still, you want to keep from bending the leadouts, because that's wear & tear, and takes some force to do. The CG is therefore the perfect location, but then that gets adjusted, sometimes a lot. Finally, you need some room, and as much strength as you can find in there, so the spar is the final answer. Just ahead, just behind, whichever fits best.

Engine and rudder offset are pretty much old fashioned notions that have been proven to be a detriment. What you want is constant line tension. To do that, you need to keep the speed constant. A good engine helps, but so does making the plane fly tangent to the circle...less drag. Props make a ton of difference!
  Steve

AmberT,

Note: all the designs Jim T mentioned are w/o operating flaps. Seems a "slightly forward" CG goes well with unflapped models, while flaps and large% tails go nicely with CG further aft.

There is a 'natural' offset compared to the air we fly in when the fuselage has thrust line and vertical fin/rudder area all in a straight line, structurally.

We want as little of that offset as possible - which to me means we want the fuselage centerline perpendicular AT the CG to an imaginary line from the handle ... not the actual line traced by the lines, as they sag aft due to drag, and - much less - down due to their weight.

Since the model flies a curved path, the engine and the fin/rudder are actually pointed 'out' slightly in relation to the air they fly through, when the imaginary line to CG is perpendicular to the fuse C/L. The angle isn't much... about 2° or (usually) less at the prop, and about 2°+ at the fin/rudder. For many models that is plenty.

When the leadout locations 'aim' the pull force to the CG with the model aligned at the right angle mentioned above, leadouts actually will be behind the imaginary line I referred to.

Jim,

Agreed on the "why" (tail volume), and apologize for not catching that you mentioned a few designed-for-flaps types in your list.

To go the other way a bit, the quite aft CGs we see on many recent top level stunters goes with the MUCH larger tail volume that's become dominant. The horiz tail is as effective as stabilizer as as elevator, and has plenty of power in either function.