If you take a trip over to O.L.Adcock web page and read down through his bow tuning page he has a great deal of info on arrow tuning and that will show you formulas for finding the right arrow, and i would also suggest getting the arrow tuning field points through 3 rivers, that will give you a range of tips from 100gr. through 250gr. which will also help when building a new shaft or find out spine problems with shafts that you already use, the bare shaft/fletched shaft test on O.L.Adcock page really helped me find out i was way over spine and with the adjustable point kit i got from 3 Rivers i can take a shaft and make them fit my set up perfect, i was using 2114 and after doing the test i found out i needed a 1916 so as you can see from my test i was way out of the bell curve of being in tune. Right now i am going to switch over to 2013's so i have a set full length with fletch and non fletched arrows and will keep shooting and trimming until i get the un-fletched and fletched hitting in the same spot and i have found that doing this test with BH it made my confidence level grow to where i have opened my kill range up to 30 yards, well i hope this helps out some, i have spent hours in the shop trying this with several bows if you need any more help let me know