It's not safe to do with a downloaded bios file I guess? I don't have windows on my UX31 anymore to extract -> patch -> and apply.
I tried doing that way before, the issue was that PMPatch increases the file size for a BIOS update. The max size that an UX32VD takes is 6MB, and anything larger will cause the update utility to deem it as "invalid/corrupt". The best way is to taker dump of your BIOS on Windows using fptw64, PMPatch, and reapply via fptw64.