I'd posted this inside another thread, but realized the information probably deserves its own thread.
Got these done a few weeks ago, and they have worked out quite well.
Used a melamine serving tray from KMart (fairly light weight compared to pizza pans) ($4.99 ea):
Drilled out the acorn nuts and epoxied in some washers plus smaller nuts inside:
They're actually all centered... just looks off:
Epoxy is setting now... using bolts & nuts to hold the nuts inside straight:
Lug nuts ready to go back on the car:
And now back on the car:
Drilled 4 matching holes into the serving tray:
The design of the bottom of the tray made it exceptionally easy to mark 4 evenly spaced lines and the center point. Measuring 50mm (5cm) out from the center to get to the same spacing as the 4x100 lug nuts was a snap. All the holes have lined up with all the lug nuts perfectly twice so far (left and right covers).
Hot-glued washers and spacers to the wheel side of the tray so they don't keep falling off during the mounting (it ain't purty, but it works):
Initially, the tray was a little big and rested on the edge of the rim:
I didn't like that, so I sanded the edges of the tray down until it fit exactly inside the edge of the rim:
Final look is pretty decent; plan to also sand down the ridges so the whole 'bottom' / outside of the tray is smooth, and then will likely paint them. Also plan to smooth the edges of the washers so they don't present such a sharp edge:
For these covers, I prefer to remove the clip-on weights on the outside of the wheel and have the tire shop re-balance with the stick-ons (or clip-ons on the inside only) so that I don't need to cut notches into the covers just for the weights. Since it's a relatively quick 4 phillips screw on / off process, and since the tires are holding air really well, I'm not too worried about having an opening for the air valve.