Tex,
I didn't want to say it because you are having some good results, but I think your 5575's might be underspined as well, but they might be closer than the Axis400's. I had the exact same arrows myself and they were erratic to the point of giving me flyers. I went to a 75gr head and they disappeared. I don't believe that Gold tip chart. I think they are a bit weaker than stated.
I subsequently moved up to a 7595 , and with a 100gr head they flew like darts.

That said I'm not the shaft/spine expert around here........maybe JeffB will see this and throw his 2 pennies in as he knows his stuff with respect to these 2 styles of shafts better than I do.