You'll want the slowest powders for the parent to make the AI work the best. Watch the chronograph, when you hit 150-250 fps above parent, you're maxed out.
Without pressure testing equipment you have no real idea what pressures you're operating at.
Usually 2% more powder over max is the stopping point.
I agree for the most part with the above posted by Mr. McDowell.
As for the powder though I might not go to the slowest, but I would sure go slower. Like if your already using H4350, you might drop down to something like H4831, but maybe not H1000.
The second part about pressure I wholeheartedly agree with. With the AI cases the straightened out sides will hold the cases in place and not give you as accurate a reading as you might get from one which still had the tapered body, and moves some. The best route to go is like mentioned to watch your velocity and give yourself 150-200fps above what your getting with standard ammo.
That said barrel length will also play into this as well, where as your 22" barrel would be a bit faster if it were say 26, and in that case you might also benefit FROM using something like H1000 verses H4831. But being you have what you have, I would stick to the above paragraph and go with the velocity and call it good.
I built my 25-06 AI using a 28" barrel. I did so to wring out about all I could from the case capacity and using the slowest powder that would give me decent velocity and good groups. I built it expressly to shoot heavy for caliber standard and custom made bullets in the 120 and 130gr range, which it does very nicely. With the standard loads I use in my regular 25-06 I am getting around 3200fps with the 115gr Partition. With the 120's in the AI version I am getting 3250 with what I am calling my MAX load. While this might not seem like much of an improvement over what I had, in the standard version I NEVER broke 3000fps with 120's without ironing out primers, and the 130's never got above 2875 before seeing the same thing. With the longer barrel I can run both the 120 and the 130's up into the 3200fps range and still get quarter sized groups at 300yds. This was my goal, and anything I might be able to go above and beyond is simply not important to me.