Doing similar. I don't normally post WIP pics because it jinxes my projects and I never finish them then. (Looking at you dinosaur costume...). But am in a similarly "stuck" situation and looking for advice/thoughts on the undersuit. Clearly the 2500's have more interesting fabric than we do in 2020...
So I did build a duct-tape dummy. Then using an old dive skin, added some muscle (because I've got covid body now) and have covered it with a stretch hex-pattern from Yana at a fabric store. That has worked out fine so far. The confusion for me is that the foam templates in the armory don't quite match the reference pictures. And in the reference pics its not clear to me what could/should be foam and what could/should remain fabric. Obviously the easy way would be to leave it all fabric and just build the "top" armor. This isn't the 501st after all, no one is going to grade you. But I like the challenge of this build, so am going to try for a little more to this techsuit.
So looking at the reference pics again, it would appear to me that if you made all of the "white" parts out of foam, you wouldn't be able to move. So I'm leaning the direction now of making a second layer of fabric, but inside-out so that there is a minor distinction between it and the "normal" fabric. Then for certain significant parts (deltoid, some chest, back and thigh) pieces, I'll use thin EVA with the inverse fabric glued to it to make it stand-out but still have the hex pattern. Then there are a few parts that'll be thin EVA with plasti-dip rubber compound for those areas that have that rubber look. Hopefully this will let me retain some mobility in my arms and legs while being a little more "screen-accurate".
Attached is a pic of the almost complete fabric suit. You can see the dive skin with my bonus muscles and the hex fabric.
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