Take a look at the exploded diagram in the back of the manual. The feathering spindle is the shaft the blade grips mount on. The blade grip mounting screws should be secured with loctite. There should be no play at this point.
The spindle goes thru some o-rings in the center hub. There are some tiny shims and step washers in here. The whole spindle/grip assembly should be able to rock a bit in the o-rings, but there shouldn't really be any side-to-side play, the shims are supposed to take care of that.
On mine if I pulled really hard, I could actually get the grip bearings to slip a little and cause play. Solution: don't pull so hard.
The blades themselves should be tight, but loose. I mean loose, but tight. Oh, heck, the manual says "moderate pressure", you'll figure it out.