has anyone tried building it already? if so, how's it and are there any additional parts required apart from the topre housing? and also how does the daughter board fit since hhkb 2 has two usb a ports?
They are pretty decent.
I've ordered additional CF plate and got hardware included (screws and standoffs) enough to build at least another one and have some spares. So, apart from the donor board itself nothing is really required.
Additional USB ports are not interfering with the case, as originally they are deeper than case back face, so it's not an issue at all.
Two downsides I've had are pretty expected: the on/off switch of Yang's controller is not accessible anymore and I've had to change my 3000 mAh battery to 1400 one, as the battery cut is much narrower. It's quite deep though, so probably gonna find some other battery: fatter, narrower and longer.
Oh, and my older T430 can't detect the board anymore. X1 carbon though works fine.