>>10603493not going to work, because Robbie is a mutant freak and would stand 8" if the line was 1:18 scale
Primarchs are bigger than the normal and extra normal Space Marines. So since Joytoy's scale is completely fucked up, you need a 1:15" scale head. Not 1:12 nor 1:18.
but who really knows how it'll actually look, given the proportions on them are all weird anyway. Buy 2 heads from different scales and decide if bobbleheaded or pinheaded works.