One online source lists the case capacity of the 30/30 as being 44.4 grains of water. They list the 30/30AI as 45.4 grains, an increase of only 2.2%. I have no way to verify those numbers. The improved version does move the shoulder forward very slightly and shorten the neck by about .087".
What Ackley claimed is that the improved case shape would handle pressure much better than the original tapered case, he said it greatly reduced back thrust on the bolt. He never denied that his improved loads ran higher pressure but claimed the improved case could better handle the higher pressure. Ackley did pressure test many, if not all loads.
At best the 30/30AI may be good for 200fps over the standard 30/30. I really doubt one could detect the difference either in trajectory or much less in results on game. I really like the 30/30 A I (As Is), it is such a generally satisfactory cartridge that I don't think it needs any "improvement".