EF,

Profile is a good way to start. You can build the bellcrank through the fuselage, and later convert that mounting plate to a mechanical 3-line system, or an on-board electronic system. The lines will be outside the wing, however. That's a relatively slight disadvantage, considering the obvious advantages for converting it to whatever throttle or other functions you want to try.

And, yes, as others have mentioned, the added drag of a third line - particularly an insulated 3d line - is often simply offset by shortening the radius by 5% or 10%. If YOU can handle the changed lap-time, where's the problem?

Luck!