Don't know why anybody would consider a 340 spine overspined. IMO I'd say it's pretty close to optimum.

Now the sight problem. OK, so you're shooting 10 yards--most likely to make sure you hit at least close for starters. If you're shooting a little to the right then I'd say move the pin (sight) a little to the right till you are hitting dead center for windage. Then shoot 20 yards to check yourself out. If you're still good at 20 yards then try sighting in another pin for 30 yards, then 40 yards (assuming your ability allows for it).

Don't worry if your pins are to the right of the string/arrow as eyed from the back. This is quite normal.

If your bow is sighted in for 20 yards really well, but off a bit for windage at longer yardages then you probably need to tweak the rest a little for windage. This can be done first by doing a search on walkback tuning.