Except Carcerian, that custom base item helmets are not possible without an engine hack which Sinfar probably won't make public as usually...
Incorrect, only standard hotu-1.69 scripting is needed to make them work.
(FYI: I actually made the first proto-type pictured above independently for Mav several months before i ever signed up for Sinfar's builder team)
In fact, I'm fairly certain they also pre-date the new SinfarX.dll/client loader technology by at least a year or more...
(Dll allows mdl scaling and tilting, and supports new body parts like torso2 etc, but heads2 are just helmets, the same as CEPs tiger/wolf helms)