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.
I am impressed that the edges of your build plate are hot enough to keep the corners from curling up. This is a problem I fight on any print that is close to an edge.
I can't speak for other printers, but my X-Max 3 has an absurdly thick aluminum plate under there which seems to spread the heat pretty well. I've poked it with my little IR camera and it's not 100% even but it's not bad. The only side effect of this is that it takes a month of Sundays to fully reach temperature, especially when you're aiming for higher temperature materials like ABS.
Here it is on today's preheat for PLA:
(IR cat tax paid here.)
The stock 350mm Voron bed is 5/16" (8mm) thick. It's quite hefty lol
WOW! That is super even. I looked at mine with a FLIR attached to my phone, and it had definite hot spots. It might be time for a new heat bed.
A cooler bed can prevent warping. But a warmer bed may be better for overall plate adhesion.