We do a lot of halter obstacle classes at all kinds of shows and have encountered one of the large teeter-totter bridges such as you see at the World Show. I have no idea how to make one like that, but we did make a smaller version that uses a round PVC pipe as the fulcrum. and produces the same sensation of the teeter-totter. The only time one of our minis encountered the large teeter-totter bridge she went right over it and won the class. I really don't feel it is necessary to create each and every obstacle you might encounter. As Performancemini said, the most important thing is to work with the mini a LOT with everything you can find so that they gain your trust. In that same trail class with the big bridge was a cage full if chickens. Our mini walked right by the chickens too, even though she had never seen one before! Now, we did have a pigeon get into our yard not too long before that, and while it was "visiting" I made sure that all the minis got to see and walk by it. So, you take advantage of opportunities too. One of the scariest obstacles (and I did make one of these) is the "waterfall" or streamer obstacle that you have to walk under/through. The first time Princess encountered one in a show (before we had one at home) she walked through it fine, but a streamer caught on her halter somehow and she pulled the whole thing down on us as she walked under it!!! She had another class to go, and because of that incident they let us practice a bit before the next class, and while she was initially reluctant to go through it again, she did OK in the next class too.
If you watched the World or National obstacle classes, I think you will find that elevated poles are one of the most difficult obstacles to do correctly, and of course ground tying next to a bale of hay is a major challenge. Many horses knocked over the elevated pole in the sidepass obstacle, just walking out after a nice sidepass.
