The rubber piece doesn't go in well
The case is great, and the mount is all fine, except that the rubber piece doesn't quite fit. It's a little too fat for my stem fork, though only by a fraction. In this case, there isn't much I can do. Maybe I could try pounding it in with a rubber mallet, but then I wouldn't ever be able to remove it.
In some ways, this device as a whole has a general problem: you want the thing to be super snug while riding, but if it is super snug, putting it in and taking it out are very difficult.
My plan is to use a different stem fork mounting bolt but use this case. The case itself is perfect for a large smart phone plus charger, provided your charger is more flat than cubic.