I think this gets to be a bit of a
complex aerodynamic Question. Rudder or any trim offers some drag,
however if it aligns the body of the aircraft more with the airstream,
there could be an overall reduction in drag. I would hesitate to
offset the vertical stab. Here's my reason.
1. Any fixed trim is generally
only good for one airspeed and power setting, so unless you never
intend or think your gear box, prop or engine is going to change I
wouldn't try to compensate with vertical stab. Once it set, it a lot
of work to change.
2. Cockpit trim is of course
the ideal, but then you may have to rig up something to drive the trim
tab, worry about what that might do to flutter points, etc. this one
takes time, money and effort to get it right.
3. An adjustable trim (such as a
rudder trim tab) can be adjusted to take care of such changes as
mentioned in 1 above
All in all, its hard to beat a
trim tab for adjustability, weight, cost, and ease of application and
since a vertical stab orientation or a trim tab are both only idea for
one airspeed and the tab is much easier to adjust - I would vote for it.