Internal timber panelling

I got a design in mind using new 18mm ply boards, left from other projects. So the workshop has been boarded out and now I'm marking up the walls with masking tape to see how big to cut the 'panel lines'.

Using a router, I'll cut these lines to hide joins between boards, fixing screws and hopefully give it a more impressive appearance.....well that's the, it all comes down to the finishing quality!