Doug,
The original Corsair (profile) flew with no offset and had an adjustable rudder which was offset possibly 3/8".  Flew well that way.  These days, I prefer just a little engine offset so that is why there was 2 degrees shown on my original plans.  Brodak may have set the engine with no offset.  I suspect that a zero degree offset on the engine thrust would still be good and line sweep and rudder will get things well adjusted.
I would recommend making the rudder hinged with an adjustable linkage so it can be altered to find the happiest setting. 
Pat Johnston
Skunk Works.

 I'd mount the engine O/O and like Pat suggests, make the rudder adjustable. Good plan for most any good sized Stunter.

 I have serious doubts about the Saito .40 being enough power for the design though, in fact I'll say it's not. I'd strongly suggest the .56 or .62.