I make depth contour lake maps of local lakes. I've been making them in various sizes of 9", 11", and 14" wide. I got a request to make one about 4' x 2', which meant it would need to be carved in at least two pieces. This was the first time I had done this, although many others have made large signs this way. I used layout tips by Michael T and left about a quarter of an inch overlap on the joined edge, which I trimmed to exact fit with my table saw. I was very pleased with the result.
The wood is New Zealand pine, which Al recently commented on in another thread. It carves well, has no knots, and is very straight with no warping. If you're careful it can be difficult to see the glue line when edge gluing.
When I carved the top half, I didn't bother to delete the centerline lettering. I was surprised when the machine prompted for the V bit, but I obliged, and the machine air carved in one dimension off to the side of the board! Next time I will delete the lettering. Likewise, the oval cutout air carved off to the side of the board in a straight line.
I did not actually use a complete cut through for the cutout. My thinking was that it is much easier to clamp straight boards than oval ones. I did not trust tabs to be sufficient. So I cut only 1/2" through, glued and clamped, then cut the oval completely through but slightly oversize using a handheld scroll saw. The edge was trimmed with a conventional router trim bit to complete the cut.