Practice your one hand stops at the walk so he will understand what you are doing.
Remember...sit deep, reach down and smoothly DRAW, not pull ,your hand to your hip.
While doing that use your inside leg, behind the girth to dis-engage his hind quarters.
When his front feet stop, release.
If you practice this at the walk, jog he should understand what your body is asking.
Then I would try it at the lope when there isn't any distractions.
If you have never done a proper one hand stop, yes, you could get into trouble.
Repetition and body language, but remember, proper warm up and suppleing helps before you start.
Have fun :bigsmiley.png: