The helmet shown in the pic is just a hack I did (it's a remix which I found on Thingiverse - credit to the original designers below). Since I don't know how to work with editing STL's (I work with IGES and STEP mainly), I had to use the slicer to make the pockets in the helmet for it to fit the Dummy 13 model. But if I can figure out how to modify the STL's without using a slicer hack (negative object), I will post a remix of the helmet as well (no guarantees though). If I could find a good helmet design as a STEP or IGES with a sharing license that would be better suited for my workflow, but so far I have not found that. Also on the table is making one from scratch, though I don't have time to do that before Christmas, so I'm gonna do the hacky thing using the slicer, just to get some figures completed.
The helmet design is credit to Renward@Thingiverse, who shared the following remix:
Halo Infinite Master Cheif Helmet(Filled)
The above model is a remix of Kolinc@Thingivserse who shared the original helmet model:
Halo Infinite Master Chief Helmet
In the meantime, here are some pics of the prototype, which had a run in with some of the other Dummy 13 models on my shelf. Everyone is cool now, and they made up, after the Halo guy cooled off. Apparently the whole thing was a big misunderstanding about roles and responsibilities, and most importantly, mutual respect. All I can say is that it's a good thing the Tick never takes a day off.
You can find it here (and Merry Christmas!)