When I run "make install", the kernel is installed to my CURRENT /boot When I run "genkernel initramfs", it searches my fstab and automounts a completely different /boot, stashes the initramfs there, and then unmounts /boot. So grub-mkconfig then screws up because the kernel and matching initramfs are in two completely different places. AND I DIDN'T DO ANYTHING TO /BOOT !!! (This is on top of my other gripe with genkernel - it creates an initramfs for the currently selected kernel, not the new kernel you're building - this has screwed me over a couple of times) (The reason for doing this is I have ONE logical disk, so I can only have one grub, and I have multiple linuxes in lvm partitions. I DON'T WANT ANY DISTRO mucking about with the master boot - SUSE auto-updated and left me needing to patch grub.cfg in the systemd recovery console because it completely fucked every option. Now gentoo is trying to be clever and leaving me with a fucked up grub.cfg that won't boot gentoo because there's no initramfs!)
Discovered various genkernel options that enable getting round it.