But, Alex, in your video, how do you move "your" head there? I assume by using the default FSX key commands.
The effect will be the same as doing it with TrackIR.

But I'll do another shot where I just use those FSX commands or the joystick pan switch, ok? Maybe this is the key aspect here. I'll report back soon.

Alex, (sadly), you are right. I'm actually using EZCA together with TrackIR and if I move my viewpoint with one of those tools (EZCA would be keyboard/joystick based while TrackIR tracks your head), the HUD doesn't stay aligned/follow.
If I use the default FSX keyboard commands, it stays aligned.
Since those other birds I've mentioned (which offer a collimated HUD too) actually work with EZCA and TrackIR, I'll place my wish on the list to make this stuff work with the CS gauge.

Of course, this is a fun product and it's not very expensive, so I'm ok here, but if it should advance in development, this TrackIR and EZCA compatible collimation would be very appreciated. I think that those two addons are very common around flight sim people, especially the military flying ones.

Thanks for your help here, I was really wondering what I could have done wrong when installing.
So this is solved and maybe it should be pointed out that the very good collimation feature currently doesn't support TrackIR and/or EZCA head movement.

I'll therefore change the thread title.