Drive 2 nails in a board 26" apart. take a known good arrow and set it on the nails. hang about a 2 lb weight from the middle and mark the lowest point (on the board) of the bend in the shaft. See if the new shafts match the mark. This would be a good approach to use as you are working down the diameter of the shaft. Or Like Sailordad said, make em and shoot em. The weak ones are for kids bows.
Chuck S.