Hi,
there's lots already done on here.
One way is find the best arrow that you have, then get a long bit of wood put two nails in it 26in apart,then get a drinks bottle that can hold upto 2lb of water and put a hook onto it. Then put the arrow on the nails,place the 2lb weight in the middle of the arrow and mark on the wood were the arrow bends to. Then all you have to do is match allother shafts to your best flying arrow......
It's late here 140a.m. and i've had a drink or two so let me know if you need any moer info...........