Regarding fear, when cutting the walnut, I understand why. Not an inexpensive material. I use Easel, and have not had any problems with the depth and tabs. Just be sure that the material is flat, and that the router’s Z axis is moving freely. cleaning the sleeve and router, and applying a silicone spray really helps. And don’t forget to attanch the small bungee or rubber bands to the top of the router to provided a constant downward pressure on the Z axis linkage… a lotta slop in that thing.
Perhaps cut the letters first before cutting the parimeter… That way if something goes wrong, you can flip it over and give the letters another go.
Look forward to seeing the finished product!