The thermal relief on the header ground pins makes it much easier to hand solder. The higher thermal resistance slows down the heat going to the big ground plane that has a high heat capacity. It’s kind of like the hole in the pad. The thermal relief goes against your OCD. :-). I did make the hole in the pad a quarter mm for highest possible thermal resistance.
I’m trying to changed to solid PADs because I’m finding that I’m not as accurate at lining up both sides for a ‘sandwich’ transfer.
Use your drill map to drill the holes first, then align your copper layers for a best fit with the holes.
I’m playing with this method: http://www.electro-tech-online.com/threads/pcb-toner-transfer-by-metal-plate-method.151020/#post-1309537
and I tried your suggestion, but the holes in the PCB cut holes in the silicon sheets, so I stopped that.
I’m just warming the etch bath up for the latest test. I lined up the holes in the ‘transfer sandwich’ pair and stuck them with small labels folder round two edges.
Also it needs two passes through the toaster