How well the trapeze will hold is dependant on what sticks you are using. But you can use any sticks theoretically. My guess would be you're using Xtremes. The only thing I can thing of is try to keep the stick (with the trapeze around it) pointing at the axle, hopefully this'll stop it slipping down.
With my carbons a trapeze worked fine first time I ever tried it. I keep the my thumb inbetween the two sticks to keep them apart. So try that.