Walt,

Let's see if I can get to all of your questions. On the Twin-Air .25 prototype shown, the rudder line and elevator line are in-line. This necessitated trimming the ends of the elevator to account for the rudder's travel inboard. I never noticed any adverse problems by having the control rod for the rudders right next to the hinge line for the elevator. Though I suspect it accounted for a little whistling now and again.

As for the design posted here, I have moved the rudder inboard from the ends of the h. stab. This strengthens the joints between the fin and the stab. By doing this I also needed to change the rudder so that I did not lose so much elevator area. So the rudder hinge line moved forward and the rudder moved up above the stab. To keep the looks up, I also maintained the shape of the fin/rudder with a sub-fin under the stab -- which has its own benefits.

As for the rudder differential. That's a tough one. The math is right in that differential will help in turns by reducing drag on one rudder while increasing throw on the other. The practical problem is achieving differential in a model this size is going to cost you in weight and in complexity. Maybe its for the .60 size, but I'd go with parallel movement rudders on the .45.

John
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There's something in the Air!