I have a flybarred Trex 500. I remember there being a bit of slop in the head. I could hold the skids and pull up on the head and it would move up and down a bit. In my "extra parts" bag, there were a few shims....very very thin washers. After putting one of those in place, the slop was much much less and I've been flying it ever since with the shim in place.
I'd suggest trying to find one of these little shims and put it in place. The, on the bench, just pull up and down on the head to see if the slop is better or the same. If it's better...take it out for a bit of a hover and see what you think.