Anyone know how to mod / load Option ROM from BIOS Holes?

According to this page and this page, it appears to be possible to load Option ROMs out of BIOS Holes if they’re too big to fit in one of the regular spots.
Does anyone know how to do this? I’ve got an Option ROM that’s too large to fit into the PXE. MMTools has a specific feature to do something like this, but I’m looking at Lenovo BIOSes so unfortunately that won’t work here.
Any ideas?