The helmet and mask only fit together if the mask is raised from the surface. To solve this issue I 'designed' this stand.
As you can see I used the 'True Sith Empire' logo instead of the regular Empire logo,... I had my reasons.
The helmet and mask can be found here:
https://www.prusaprinters.org/prints/31565-wearable-darth-vader-helmet
The author marked this model as their own original creation.