I updated to rc5 from rc3 and the gpu passthrough would not work despite it working before the update. I then tried changing the ram parameter under for the stubroot method to 1.5GB, 1.75GB, 1.95GB, and then to 2GB (the original value that worked on rc3) and it worked again. I don’t have a clue as to why this would work, but it did for anyone who might run to a similar issue.