OK, apologies, got a bit distracted trying to finish another job yesterday & didn't get to your wood 'til this morning. Couldn't find any bits of Qld Walnut big enough, but here are two other possibilities for you.
Attachment 517219
The two top pieces are Cardwellia, the bottom is a bit of (figured, as you can see) Qld maple.
The top piece of Cardwellia is 25mm thick but face-cut so the medullary rays are all edge-on. The middle bit is quartered, showing the ray-fleck nicely, but is only 18mm thick. The Maple is about 19.5 thick, but a bit rough on the other face. If any suit, you can have any or all - postage will probably be the same whether I send one or two or three.... :)
Cheers,
Ian