After some careful research and planning I went ahead and cut the holes in the dulcimer sound board.
The design is a mirror image of the other side and since the walnut was book matched I was able to lay the finished sides of the sound board face-to-face. This ensured that a majority of the chip-out would be on the underside of the sound board and not the finished side. This also strengthened the wood while cutting and cut my work in half.
Even with chip-out precautions I had some chip-out. But they aren’t too bad and I’ve already patched them.
Here is a photo of the leaf holes cut, before I patched the chip-out.