Thanks.
I have built mine. Didn’t use the USB-C connector, powering the RPI4 directly.
Voltages: I get the 5v and 3.3 from the Vreg correctly (it looks like it’s working), but I only measure 0.05V when the RPI is coonnected on the test point below the screen… (???)
RPI light is always red…but If i disconnect it the lighst are red/grren, so it’s not dead at least…
SOLVED: I had a very small short on pins 27-28 of the 8731