Dear Crazyengineer,
Looks ok to me. Those slotted aluminum pieces have been pretty sturdy in my experience. They also bolt together tightly, so it shouldn't wobble too much.
The only thing that I could imagine failing would be the plate on the bottom. It you're planning on having that support weight you'll probably want some crossbars. If it's a thin sheet held on by a few bolts, the bolts are liable to tear right through it if enough weight is put in the center.
~Tom