How do I create a mirrored system disk in Solaris 10 jumpstart?

Solaris 10 supports the use of mirror devices with the filesys keyword. This is in addition to other new features including patch installation, and package commands (when installing flash archives).
Here is an example jumpstart profile with mirroring:-

install_type initial_install
system_type standalone
cluster SUNWCall
partitioning explicit
filesys mirror:d10 c0t0d0s0 c0t1d0s0 8192 /
filesys mirror:d20 c0t0d0s1 c0t1d0s1 4096 swap
filesysmirror:d30 c0t0d0s3 c0t1d0s3 4096 /opt
filesys mirror:d40 c0t0d0s4 c0t1d0s4 8192 /usr
filesys mirror:d50 c0t0d0s5 c0t1d0s5 free /export/home
metadb c0t1d0s7 size 8192 count 3

Rather generous slice sizes, but they always seem to fill up....
The submirror devices names will be formulated automatically (e.g. d11 and d12 for the d10 mirror device)
Metastate database replicas must be on a slice separate to any metadevice (This is not a restriction other than in a jumpstart), and there must be at least three in any SVM system