I spent some time over the weekend making the RGB version of the cufflink as small as possible, in particular the PCB. The overall size is limited by the cell being 12.5mm diameter. It is differrcult to embed the fixing screws in the same way as outlines for rectangular cufflink. However I can squeeze the layers down to 5.
With the design in mind, I planned out the PCB. It was really tight to get all the routes in via freerouting . In the end I got a working PCB layout.