Oh, I forgot to report on my impression of the GDFB mail. At about 18 pounds, it's heavier than my aluminum, but not by a lot. The weight distributes well and is pretty comfortable.
It's much more difficult to put on than I'm used to, due to a combination of the sizing and the rivets catching on fabric, etc. The flat rings make the mail slightly less flexible and compressible than my aluminum set, so it tends to get really rigid and bind up on itself when trying to put it on, whereas my aluminum just slides itself into place with just gravity.
In terms of the sizing aspect, on the website they say 50" chest, and on the phone they said 48". The rule of thumb is to leave at least 4" over your actual measurement, but this technically leaves me more like 7" (I measure about 41"). Even so, it has less give than my aluminum set which is also tailored for a close fit.
It's stainless, but has a black finish. The black is flaking off all over my floor, so I'm assuming it'll wear down and be less black over time.
They didn't taper the sleeves, or have a widened base, so these are things I need to work on myself. At some point... someday when the loose links/rivets actually ship to me. In the meantime I can still taper the sleeves and just use butt-links to close the seam.
Even with the plate components and steel mail, I think this is my lightest harness so far.