In spite of a cold/allergy situation, requiring frequent naps and Sudafeds,I was able to do the stenciling fairly quickly, thanks to the use of fast-drying acrylics.
I forgot to bring a print-out of the layout, so I had to do this from memory.
The finished board is now ready to be installed. I will configure some clips, and some moldings to match the fireplace surround, in order to hold it in place.