I'll stick my neck out....
Having measured that 1 click of the No 4 rear sight moves the leaf near enough to .008", by my reckoning you could try a -.045 foresight.
Logic for this is that there are 7 clicks between 600 and 500 on the rear sight, so the sight change required is .056". Each foresight blade increment is .015", so if you came down by .060" I think you would be fairly close.
I too would be interested in how your rifle shoots at the closer ranges, and how the 6 o'clock hold issue enters the picture.
In my own case, I choose to zero (centre hold) at 100 yards; then use a 7 click elevation offset after changing sights for range to allow for the 7 inch distance between aiming mark and centre of bull.