Jason,
To my eye these casings look to have quite a bit of neck. This was the "thing"at the turn of the 19th century with the 22Hornet and 30-06 calibers... Today we know .250 is all thats required for good neck retension. To get my drift look at the 284 Winchester neck length.
Also shoulder angle, you can get more cap with a steeper shoulder, also lower pressures with min body taper, but its probably pretty good is still the base 445 dimentions..
Also, a nosy question. How are you dealing with custom die costs? They can get mighty costy...
CW