Right, so I have this thing, I'll do some testing in a bit, but here's my first impressions (which means they are to be taken with a hefty measure of salt):
Duo is low recoil defense, just like death. My duo is a bit lighter than my death, but with low recoil defense, that's not the primary concern, as can be seen in comparative tests.
In this way though, I doubt it will outclass basalt, like Death, it is a different form of defence (and "outclass" is very different to "outperform". I'd be surprised if basalt ever became "outclassed" unless a heavier wheel, or one that is very close in weight but better balanced, is released).
Duo is quite small for a 4D wheel, which I guess is something? That said, it's only 1-2mm smaller than Death so....
But yeah, I will try to get some testing done tonight, if not, tomorrow.
EDIT: 10 Rounds of it versus blitz. I'm not awesome with attackers, but the lack of recoil and decent weight makes it hard to hurt.
MF-H Duo Aquario BD145CS (Stamina) vs MF Blitz Unicorno 90R2F
1 Duo OS
2 Duo OS
3 Duo OS
4 Duo OS
5 Duo OS
6 Duo OS
7 Duo OS
8 Duo OS
9 Duo OS
10 Duo OS
Duo: 100% (OS)
Blitz: 0%
Stopped there, if I had done 20, 30, 50 rounds, whatever, Blitz would've probably got a couple of KO's, but it’s not a matchup you’d want to be facing as a blitz user.
Same CS as I use on my basalt, where it goes ape, here it barely moves. Basically, Duo is pretty well balanced. Don’t be fooled by the rattling, it’s solid.
Blitz gets SO close to KOing multiple times in each round. I love Blitz, but Duo is very low recoil (basically, it’s a death clone), and always seems to hang in there.
May be that I’m not doing well with attackers (though in the few rounds I’ve done, Blitz is throwing basalt BD145CS around and out), but yeah.
Will try to do some proper stamina matchups later, just wanted to get this down. I think Death would do basically the same here, from what I've seen of it.