In accordance with your specs, a 24XX shaft strikes me as a bit stiff. I would try a 2314 or a 2315. 5" feathers are my choice; for reasons as given by Art P, and for many other personal reasons. However, being you can't use feathers, at least try a 5" vane.

If we were running a contest for the closest guess of what a cure might be, my guess would be; 2314's and a your 100 grain head with the present size vanes you now have on your shafts. 2315's and 125 grn heads if you were to change to a 5" vane.