What distance are these bare shaft results from. Four inches left at 10 yards implies are far much stiffer arrow than 4"s left at 30 yards.
Options
1. Increase BH by 1/8-3/8", then re-evaluate
2. Increase pt wt from 50 to 150 grains and re-evaluate.
3. Lengthen arrow ~2"s,re-evalaute and progressiveley shorten
4. Try a lighter spined shaft.
5. Reduce sight plate thickness.(~5#'s arrow spine per 1/16"
May take a combination of the recommnedations to obtain perfect flight. Option 5 would definatley be my last consideration.