Adding third drive to existing raid0 set

[Tom Moore <tom@tomstroubleshooting.com>]

Hi guys.
I've got a machine with two drives in a raid0 config.
I've added a third drive to this machine. I am not using lvm.
If I want to add this third drive in to the md device how would I go 
about doing this?
I added the third drive in to the mdadm config file and set the 
partition I want to add as type fd.
Can I grow the size of the set to fill the entire combined size of all 
partitions or do I have to start over and recreate the md device from 
scratch and reload all data from a backup?

Thanks,
Tom