good point Scyth,
we find when we taper from 11/32 to 5/16 over 9" we lose about 10 grains in weight.
so for a standard arrow, with a 125gr point, reasonable fletchings and a plastic nock, due to its foc or balance point it works (according to all the tests we did) out to a ratio of 1: 1.6
in other words for every grain you add to the rear, you need to add 1.6gr to the point to maintain the same foc.
so if you remove 10gr from the rear, its the equivalent of adding 16gr to the point.
so that like going from a 125gr head to a 140 plus gr head. thats a significant improvement in foc, without actually having to add the weight.
its really a win win. you get a lighter overall mass of arrow, with an improvement in foc without actually having to go to a stiffer spine shaft and an increased mass in the arrow.
And as we know, thats better for trajectory and for " paradox" recovery, and the arrow is also inclined to be a bit more forgiving of slight errors in release.
having said all that, there are some negatives to high foc arrows too- but that a whole 'nuther discussion.
i will see if i can find the results of those measurement and tests we did, and post them up here, if anybody would like?