I tried to use GRUB2 as a payload when building coreboot for ThinkPad X201, but it's too big to fit into the rom. The GRUB2 coreboot image without modules is 2.8M and >800K after compressing, it's still too big.

I think FILO and u-boot are good alternatives but not so user-friendly and documented as GRUB2, so it's time to find a way to slim down GRUB2 as a coreboot payload.