targetbutt
Arrow size is determined by several things, the two major ones are bow weight and draw length. Then if you shoot compound, your cam type will also determine arrow size. If you shoot recurve, your release skill will also determine arrow size. Having said all that, the spine difference between the 2216 and 2217 is minimal, specially if you're shooting compound. When you use a mechanical release the variance between each shot is so small, relative to finger release, that you can shoot arrows several spine size stiffer and still be ok. Assuming both your arrows and his are the same length, all you have to do is get some slightly heavier points/broadhead and you're good to go. You do need to adjust your sight, the 2217 arrows even with the same size points will be heavier and hence drop more compared to the 2216. I wouldn't mix them due to that reason.