Improving positioning in LOITER

I’d like to see if it’s possible to improve my copter’s ability to stay in position in LOITER.

Here’s a chart of it’s current ability to stay in postion:

I don’t know if this is considered “good” or can possibly be improved.

The wiki on Loiter suggests that the PSCx parameters shouldn’t need to be changed:

Would someone please suggest a resource to learn how best to tune these or other parameters necessary to improve the ability of LOITER to stay in position.

As reference - here’s the BIN file from the chart above: