I'm assuming that with a 60" bow, you're not drawing past 28"? There are several things you can do to increase spine if you need to: shorten the arrows and add weight to the nock with a Gold Tip nock adapter and internal weights. 29" would be a good length arrow for a 28" draw, and would stiffen the arrow quite a bit. I don't think you need 7595's. But then I don't know if you need stiffer shafts either; it could be something else.
Are you drawing with a split finger string grip? Sometimes pressing down on the nock with the index finger can cause problems.
Are you sure you're not torquing the string or the bow? That is a common cause of erratic arrow flight.
I don't know if this is an option for you, but it helps a lot in working out form issues if you can practice with a light, maybe 40#, bow.