Thanks
@Headshot effect: that's strange. Do you have any additional mods enabled?
Are you getting actual headshots ("Headshot" message and all, except the effect itself)?
@ACE: yes, it's mainly the shake effect, but there may be other stuff triggering ACE kicks. It's the consequence of having 95% of the mod being processed client-side (so the server cpu and bandwidth aren't impacted by the mod).
@Mod modification: Yes, I remember someone asking permission to modify it to add new blood types and a few other things, to which I agreed to as long as he changed the package name to avoid mismatching.
But it's not originally his mod ofc, even if some players think that way.