Ok It took a bit trying to get the dome together. First made a simple cardboard template to figure out a size.
I used styrene, cut heated to shape, then rivited. That is a real simple way of saying I spent hours trying to get the plates all lined up and fit with each other!

Cut out ears, and glued in screen material, painted black.

Did all the final rivits and added top band and rings.

Then made neck with vents part out of styrene, same diameter as dome.

Don't have any pics of making the 2 lower shoulder/chest rings, but took the softer type foam pipe insulation, added the harder type pipe insulation of a smaller diameter inside bigger ring. Then basically sewed the 2 foam pieces together where the seams were. Added some stiff wire in the 2 tubes, then bent it to shape over his shoulders til' it fit and looked right, then sewed ends of pipes to each other. Here's a mock up:

Had to cut out curves from lower neck vent piece to lower down over shoulders into the foam rings. Drilled holes along the bottom line of that part, then sewed to foam. All the sewing is using saddle stitching btw, pretty tough stuff. Drilled holes near top edge of lower neck vent piece, sewed a strip of leather around it, so dome slides into that leather strip, basically sitting on top of the lower neck piece.
The rest of it is basically cutting long leather strips and adding buckles for straps. The ones through the foam were slid between the stitching. I came up a fake buckle look, with magnets. so when it's on, it loooks like the dome is really strapped down, but can easily remove dome!

The ab piece and arm are all made out of leather as well. It was a lot of work and time to figure out, sounds like it was real easy when I read through this! Also a lot of fun building him and the other ones I built.
Thanks for the interest!