Turning a slightly different circle

When you train your horse to do a circle or circle around you without use of a lunging whip, often enough it is not easy to keep the horse nicely on the track. We can use large pylons in training, for example. However, I have heard that there are candidates who overturn the pylons, or simply walk around them and come inside the circle. I also thought it was a shame to throw the old trampoline away. My original plan was to turn it vertically and use it as a giant tyre jump. But that did not work for.  Now we use it as a circle guide in the Horse-Agility course on Hof Steigerwald. That works perfectly.