I cant speak for the
SW kit, but the Ven Dread heads work fine for normal marines. They might be a tad big, but they are more heavily armored than most helmets, so it fits.
I really need to drink my coffee before I reply. How the normal Ven Dread heads fit is not very useful information, as you are asking about a very specific head. I blame the similarity in kit names and undercaffination.