Pdq 5oh may have it right on this..." Why do you believe your overspined?"

Are you getting occassional " fliers" to the right, or are you impacting to the right?

Impacting to the right can be indicative of underspine. Impacting to the left can be indicative of overspine.

Being your accurracy and grouping is good up to 25 yards, I would leave the shafts as they are for the time and look for other causes. If you were consistently going right at all yardages, of the many things I would check, would be the centering of my rest. Also, check and see if your are " canting" your bow.

Ah, archery! Nothing better if one craves confusion and frustration!