I don't yet have a 260AI but have run and still run a 260. I load for a few 6.5 creed clients. My 260 runs better than theirs velocity wise and at a lower preasure which equals better barrel life. I have a long action Ruger VT waiting to be built in a 6.5 something. Definately not a 6.5 creed but looking at the 260 AI or a 6.5x55AI or a 6.5x284.
Mag length would accommodate all of the above. I like heavy pills at lower pressures under the 3000fps range for good barrel life. Definatly like the idea of lapua brass which can be had in all 3 of those chamberings.
All of my 260 brass I made from 308 winchester cases that I neck turned, which I like to do on my match brass anyway to keep the neck thickness consistant. So fire forming to 260AI would be easy.
If I only had a short action then 260AI would be my choice no questions as my regular 260 is on a short action using MDT mags with out the binder plate and works flawlessly.