I didn't find what I thought I wanted for standoffs at the hardware store. So I ordered a kit o' plastic standoffs from Amazon instead. They'll be here Wednesday so I'll wait till then to figure out the power supply mountings.

Rather than doing nothing, I went ahead and worked on some more metal bits. I managed to get the cross rails on, and even made one of the sides too. It's past midnight now, and my wrists are screaming at me for using the nibbler thingie. So I'll try and get the other side built tomorrow, and likely the next deck for the BBB too.