Connecting Raspberry Pi 4B to Einsy headers and additional power.
Hooked up a 4B to my MK3S per the following (which is the same as the Pi Zero layout and what people seem to be doing):
Got everything running but OctoPrint doesn't like the 2.5A underpowered state.
Now, I know I can loop in a buck converter at 5V 3A from the psu, or maybe the power rail on the Einsy, but that seems too hackey.
I am pretty amatuer on electronics but I know a decent amount. The J19 RPi header is delivering 5V 2.5A to the Pi via VCC pin 2. 
What are the implications of connecting VCC pin 10 to the currently unused pin 2 (+5V) on the Pi? The Pi specs say 5A is OK.
Additionally, would I need to add another ground? It was speculated in another post that the J19 Pin-14 which connects to GPIO 23 is actually unused and only for structural integrity with the Pi Zero. Could swap that out if necessary. Anyway, hope someone who knows more than me can chime in.