Adjusting Horizontal on Bullet Camera

How do you adjust and get the right horizontal on bullet camera. Well the ACT20 don't have a screen. What I did was review it video playback while pointing at something horizontal. In my case I use my house grill and once obtained I'll mark on the clamp with reference to camera body for future mounting.

Above photo shows already mark once alignment correct. I use the camera indicator LED for reference point and mark on clamp where they should align to. This mount already good.. its vibration is minimal, I'll post ride video to Genting with this camera on this mounting.