My list of acceptable that I go by:
Anyone are free to disagree and I know some do. Some want all recasting stopped, even cast from screen used casting, others want a free-for all. With all recasting stopped, even cast from screen used... for most props, especially helmets, you'd be left with licensed wares and fan interpretations. With the free-for-all... cast from screen used will stop appearing as there would be no point in risking damaging an authentic or screen used prop if the greedy, needy masses just accepts that effort to be recast.
Since this whole hobby is pretty much illegal... it is the hobby that decides the rules for how illegal we wish to go.