I would suggest for EVA foam; you could print skeletonized forms in PLA and gluing to that. Yeah, it’d be super slick to be able to just print the stuff, but overall, rigid plastic is awkward and uncomfortable to wear.

You can sandwich the skeleton form between layers. A coarse sanding will get barges to hold every bit as well, too. And the skeleton can offer a more-solid foundation for spikey-things and such, too. And if the form is a difficult shape to print, you can also soften it quite easily with a heat gun and drape it on a form- or, if it’s a sheet use your heat bed set above 70-80 (for pla,). Bad for printing. Great for post processing.

(Also, have you made a vacuum table? You can make a cheap one using that corrugated plastic signboard stuff, and a shop vac. You can also set up a space heater as the heating element using MDF or plywood as a box frame- or a gun. You can make helmets very easily using a vac table and a 3d printed bust that’s the same size as your head.)