I know this is way late for the OP but good advice nonetheless - BACKUP BACKUP BACKUP! Don't tinker with anything with the filesystem, RAID configuration, etc.. without backing it up first, especially with a RAID0! Also, RAID is not a substitute for a good backup, even though most of the time if a single disk fails you can rebuild the array without error/downtime, if you have a multiple disk failure, or if power is interrupted whilst the array is rebuilding, your only solution may be restore from a backup.
Should your controller not support an array transformation, you may be able to transform it using CloneZilla (www.clonezilla.org), the key is if the array shows up as a device vs if it shows the individual disks in the array (Some "FakeRAID" type controllers do this; on my HP system the SATA RAID controller shows each disk where the SAS RAID controller presents the array as a block device). If it shows the array as a block device, you can clone the disk to an external or spare hard drive, then after verifying it's correctly cloned, rebuild the array from scratch with the new configuration, and then restore the cloned image back to the array.