My plank was bigger, but it ripped it in half, because it was so twisted, that it would yield maybe 25-30 mm thickness if I did not rip it. Now I have 40 mm. I will construct it in a way that the top can be removed, so that I can replace it for some 70 - 80 mm slabs later in the future.That plank is quite small though, hence the suggestion to use your bench as a reference,
for speed and ease.
Planing something like what you said though, and it's back to Charlesworth for me.