Alternatively, can disktab be used? The documentation is not entirely transparent on this, but it does appear that disktab might be able to override BIOS parameters.
Apparently not. disktab looks like it's mostly used by disklabel. It turns out disklabel with -e will let you edit the geometry, but the kernel doesn't actually change the values it uses for drive access, even though the disklabel remains correct/consistent upon reload.
