Hi Captain, A prescribed setup for the "right" hole on the chain plate is not possible - too different are mainsheet systems, tolerances and other factors (racing vs. recreational sailing).
In a way you already answered your question. You have created a good amount of mast rake resulting in unreasonable wetherhelm - you have described what could be done to compensate for it (rudder rake adjustment).
The limit for mast rake is pretty much when upper und lower mainsheet block touch. This is a setup that you could adjust anywhere (e.g. in your driveway on a still day). The rudder rake adjustment is more difficult - especially on a non-adjustable casting. You mentioned the re-drilling option (difficult since there is a lot of guess work and you have only one chance to get it right) or the upgrade to an adjustable casting ($$$)

Patrick