Chromebook snow: How do I change kernel commandline options?

[Veyrdite]

When I followed the old installation instructions a copy of u-boot was installed to a partition With the new installation instructions this is no-longer done.

With u-boot I could change common_bootargs. Is there a way of changing them now without recompiling the kernel? I presume vmlinux.kpart is checksummed, so I can't just hex edit it without bricking my system.