I just looked again at the second photo. I saw a board with dowels in it, I mistakenly thought it was a 'breadboard' end. Anty, I looked at it again, this time looking at the grain pattern on the end. Although not ideal, it dont look all that problematic. Ideally, the end grain should be dead flat. Good luck with that happening. Anway, just for knowledge purposes, If a board is going to 'cup', look at the end grain and envision the grain trying to straighten itself flat. That will be the direction of the cupping.
Next time if at all possible, purchase a 'moisture gauge' and also, find a new source for your lumber.
Here is one possible solution: IF the wood stabilizes in a week or so, and you can live with the slight cup, you can get a contrasting wood and make maybe just one or 2 'butterflies' to go across the split. It is quite common in modern custom furniture.
I also would scrap the idea of a waterfall.
In the US where most members are located, we refer to oven dried as "Kiln Dried", however; dont change your vocabulary because of us. Just stated that to get familiar with our terminology so if u see it you will know what we are talking about. Obviously, we all understood what you meant by oven dried.
Tony B Retired woodworker, among other things.
"Strive for excellence and settle for completion" Tony B
Last edited by Tony B; 06-01-2020 at 03:52 PM.