I am currently building project guns in both 8x57 and 8mm-06AI - I don't know about 8mm Mag performance but I do think you can push 190-215 grain bullets at more than proportionally higher velocities than with the 8x57 - the 8x57 will do everything you need with 150-190 grain bullets - I happened to obtain two sporter barrel blanks so I'm going with a 20" iron-sight, mannlicher with the 8x57 and a full 25-26" sporter with the 8mm-06AI. Since anything other than an 8x57, 8mm norma, or 8mm mag is a wildcat, make your own brass proposition anyway, why not go with the improved case over the regular 06 version - at least that is my reasoning. Also, the full ackley improved case is a straighter tube and results with less recoil/thrust issues with your cases - I have (2) 280AI's and a 30-06AI, and I get great case life compared to conventional 06-based calibers I load.
As I build load experience with this caliber, I will be happy to share my results with you - I do have a magneto chrony so I can also give you velocities I obtain. My email is firstname.lastname@example.org
and we can continue discussion on that venue if you like.