The fact is that sloppy linkages give you... sloppy linkages. Potentiometers designed for a different application give you...lousy centering. Hitech 605, 645 have lousy centering. They are not recommended for use in multiple servo applications. That is most noticable when they're ganged up on an aileron or you run 2 elevator servos. My criticism of them is that they are difficult to match in speed and endpoints. Are they any worse than Futaba or JR? NO! The 605's and 645's just aren't well suited for this purpose. Especially when you're running +/- 45 deg. and it becomes really exagerated.
FWIW: I've seen ganged JR's on a Fiberclassics Extra pull 1 Amp at idle because they were fighting each other. Even the pro's don't get it right, they get it close.
On my Cap 1/4 I replaced the Futaba 9403's with Hitech 5925's. For my 1/3 Cap I just picked up (6) HS-5925's, (2) HS-5945's and the programmer.
I think that the 605's are just fine for aileron and elevator if you're on 6v. You'll need close to 100 in/oz for rudder though. Like I said before the biggest problem is getting the elevators matched when you run them independently.