Since people wanted to see how it turned out. This is a 330x330 object that covers the entire purported print area of my machine.
I'm ashamed to admit that I undershot my filament usage calculation slightly, and I chickened out just before the finish line. I didn't have any more white in stock, so I switched to some grey of the same type from the same manufacturer by doing a mid-air refuel, shoving the end of the new spool in chasing behind the very tail of the old one. I don't think it looks too bad. I may just spraypaint the entire thing white later anyhow. I wanted to use a light color in order to more easily spot and keep track of screws and springs and such.
It certainly makes it easier to photograph, or at least to find with the autofocus.
There are also two color blemishes on the top surface which I'm a little miffed about, since these were defects directly in the spool of filament. It must have been made with like two pellets of the wrong stuff in the hopper.
Oh well. It's a tool, it's not like I'm hanging it up on the wall in a frame or something.