[Wannabe]

You'd still have to make some sort of cushion, right? Like the hideous, huge foam rings they offer?

Not necessarily. With my first version using polymer clay I found the if I sculpted the clay carefully by gently pressing it against my chest it fit so smoothly that cushioning wasn't needed. You're basically custom shaping the cup to your chest, so it just fits you perfectly. The hardness of the plastic doesn't seem to matter then.

I haven't picked up my epoxy putty just yet, but I'll check back in after I try that.