Could be wrong but I haven't been able to get that to work - the only way to really hide techs is to tie them to an alignment? |
Right, as far as I know, tieing a Tech to IMPOSSIBLETECH does not hide it, but you won't be able to research it unless you start with it, someone trades it to you, or you steal it.
Tieing a tech to an alignment will hide it from the tech tree completely, at least until you get the Tech's alignment.