Use a Dremel, or similar to cut the section off as far to the back of the cut out section as you can, then, using a set of grain scales and some decent jewellers files gently file the cut end to get them all the same weight.
Of course if you want to get that particular you might as well make sure you nock and fletch the shafts and inlude them in the weighing too. that way you can get all your arrows matched in weight.
