Migrating vinum to gvinum

[Sven Willenberger]

I have a 5.2.1 box that I want to upgrade to 5.5-RELENG and in doing so
need to upgrade/migrate the current vinum setup to gvinum. It is a
simple vinum mirror (just 2 drives with one vinum slice each). Having
done some googling on the matter I really haven't found a definitive
"best approach" to doing this. The choices would be:

1) making buildworld and making kernel. Remove the vinum-specific
entries in rc.conf and adding geom_vinum_load="YES"
to /boot/loader.conf. Rebooting and [optionally] running gvinum
saveconfig.

or 

2) clear the current vinum config (which would leave the data intact on
each part of the mirror?). Making buildworld, making kernel, adding the
loader.conf line. Then rebooting, installing world and rebuild the
gvinum device by creating a mirror with one disk and then adding the
second disk.

Anyone have experience in this migration process? Alternatively has
anyone converted a (g)vinum mirror into a gmirror setup?

Thanks

Sven