Regarding the CMC Devel/Shooting Star follower. Over the past decade or so, the follower has somewhat fallen out of favor, partially due to this movement in the tube, which can ding aluminum frames, but also partially to the introduction of longer tubes, that don't need such a space efficient follower to allow 8 rounds in the tube.
Folks often overlook a couple advantages the Devel follower has
1. There is very little surface area that the follower touches inside the tube. If you have debris in the tube, like sand or dirt, the follower is probably less prone to sticking inside the tube than some of the other follower designs that have a lot of surface area contact within the tube.
2. For servicing your magazines, the Devel follower is really easy to get out of the tube for cleaning. Some designs require a good bit more effort to remove for cleaning.
There are no perfect mags, but there are still some good features to the design.
Edit to add: Regarding flush fit mags, the topic of the thread, if you absolutely have to have 8 rounds in a flush fit mag, the Devel/Shooting Star follower is the most efficient/effective follower to allow you to squeeze 8 rounds in a tube designed to hold 7.