Ackley designed his Improved cartridges to minimize body taper and have a sharper shoulder as a way to improve powder capacity. Some got higher velocities and others did not do so well. I believe that the 35 Whelen AI falls into the latter catagory as there is just not enough extra capacity gained in the powder room.
The most significant aspect of Ackley's designs IMO is that he kept the headspace datum at the same point as exists in the unimproved cartridges, so you can fire standard rounds in the Improved chamber. Here's the good part - if the rifle shoots well, keep the current barrel and save $300+. You can buy standard 35 Whelen dies for $35 or so and have a rifle that shoots both catridges
