ManageDisksOnSystemBuses after clustering configured

I have a 2-node cluster that is already up and running. Both nodes are boot
from SAN and have all their other disks on the SAN too.

When it was built, it looks like LUN masking was used as a way round the
issue of the Cluster Config not liking the fact that the shared disks were on
the same bus as the OS disk. Now that I know about the Reg Key to allow the
cluster to have all disks on the SAN (ManageDisksOnSystemBuses), I would like
to correct this.

Is it possible to add this registry key after the cluster is configured
without having to rebuild the cluster?

Thanks.