I included a picture of how I got the flower to stay in place. I saved the piece of foam I cut out for the top of the flower and glued it to the bottom of the top of the tube. I know that sounds odd but the tube itself is a round cardboard box. Take the top off, flip it over and glue that extra piece on there.
I really enjoyed making this flower and warp tube and I am trying to figure out what my next project will be. If you have any ideas please feel free to leave a message at the bottom and let me know what you want to see. I may have to try and make a Bullet Bill or a Mario of some sorts.