“But I’m an electronics engineer, and reasonably proficient at BGA rework.”
The RAM is soldered to the board, so the 8GB model stays 8GB forever. Davill pulled LPDDR3 chips off his old laptop and reflowed them onto the new one. It booted with 16GB. His own conclusion is the real lesson: next time he will just pay Dell’s markup upfront, which is exactly what soldered RAM is designed to make you do.