Has any one tested the altitude control mode?

Recently I tested the altitude control mode,But I find the performance of it isn’t very stable.
I don’t know whether my pid parameters of altitude control is fit.
Can any one give some opinions?

I’ve done a couple of flights using altitude control. It worked quiet well. Of course you can expect some altitude change when going from hover to fast forward and to hover again. But drift was surprisingly little.
What’s the concrete problem? Craft changing altitude or bouncing up and down,…?

You look the picture