you can get 5/16 70 grain field points, taper your shafts down a little and they will fit fine. do all your tuning with like grained field points. once the arrows are flying good, then mount your stone points, shoot them only once or twice into a soft foam target to ensure they fly good... if they dont fly good then spin test, or check your point weight. there shouldn't be any flight difference between field points and stone points. as for a target, I like to use a styrafoam target from walmart.. once of those really cheap ones wrapped in plastic with the red white and blue bullseye's .. I have also made my own by purchasing a 4x8 sheet of 2" styrafoam from homedepot and cutting it in 2' x 2' squares and glueing them together at the corners with window caulk (that wont melt the foam) and also wrapping the edges with duck tape to hold them together well. in a truly primitive setting I would shoot into a sand bank, but they lightly touch up the cutting edge before hunting. fwiw- I have been experimenting with different sized stone points on deer, and I still prefer 70-90 grains. If you are shooting a lightweight bow, I would go with 7/8" 50-70 grain points. I spend way more time on arrows each summer in anticipation for the fall's hunt than I have ever spent on the bow. I have about 20 good cane arrows for my hunting bow, I am constantly adjusting them until I am super happy with perfect arrow flight. 2 weeks before season I will take the top 6-8 and mount my points on them, test once, put away, and next time they fly will be at a live animal.