Can you get your hands on h335, N530, or N135-40? The A2 isn’t temperamental, but N550-5 looks a little slow to me. Those slower powders turn the A2 into a flamethrower. Given N530 is right between IMR4895 and H4895 on Hodgdon’s burn rate chart and 458 win mag loads with the two powders look very similar, I’d simply use starter H4895 loads and back off maybe 15%. You’ll have to work up, but that doesn’t take long. Why look at the 458 data you ask? It’s a straight wall case, and the A2 is nearly so. My experience has been that predictable performance in the win mag loads is a reasonable indicator of predictable performance in the A2, but I always start a bit lower than seems necessary out of an abundance of caution.
Have you shot your A2 much? Up to about 2300 fps the recoil is profound but not truly evil. Once you step over 2400 fps, you really need to watch where you put your feet when you light one off. If you need official load data, I can get you the loads out of the A2 book, if you’d like.
This is what IMR4350 looks like.