Cheers fellas.
I got the framework for the false floor done. I used bits of the A16 chassis, mostly so it would go away, and partly so I could use some of its existing threaded inserts to mount the falsie panel:
as you can see, I offset it to allow for the motherboard tray. The top of it should end up about a quarter inch shy of the bottom of the motherboard.
Here's a couple different angles:
I didn't tie it into the rad rack because I want the inner face cover plate for that to extend down to floor for cosmetic reasons. I can't really explain it, I'll have to show you. For that, I need to start hacking up some more innocent brushed aluminum Lian Li panels.