When your Armageddon headlight is moving around the stem, please follow these steps to fix it.
1. Loosen the two bolts on the side of the stem as far as possible. Make sure they do not fall out.
2. Loosen the bolt that is located on top of your stem.
3. Push the stem down as far as possible.
4. Tighten the bolt that is located on the top of your stem.
5. Tighten the two bolts on the side of the stem again.
Now the mounting bracket of the Armageddon Headlight is sandwiched between the spacers and stem.