Built the window borders today with 3" spacing all the way around. It is 1/2" PVC painted black, and pixel holes drilled throughout on the drill press. It will be held in place using the PVC clips from Holiday Coro to make it easy to put up and take down.

Were those 12mm holes drilled in the 1/2” pvc? I’ve been concerned that would be too large of a hole. Thanks!
They are technically 1/2″ holes which comes out very close to 12mm. It works great! Drilled a bunch more that has been replacing my roof outlines.