When their tack welds were secure I pulled the wire stitches from the Dorade boxes and set about applying fillets, inside and outside the boxes.
This went quite well, using a 'pastry bag' to dispense the wood flour fillet mixture evenly.
Here is the starboard box with its external fillets.
And here are the internal fillets, on the inside of the box.
As usual and despite my best efforts, the fillets cured like roughly poured concrete. At least I know I have the right tools and techniques to reduce them to smoothly contoured joins ...