Awesome build, well done!
I'm looking for more information on your heated bed. I have a 600mm³ printer with a dual zone heated bed and a bang-bang controller. This of course is causing z-banding.
I would like to change it to pPID control and would do so using an identical design to your machine.
I can't find enough detailed information on how to parallel wire the two silicone heaters and properly ground everything.
I wonder if you could point me in the right direction?