Upgrade a RAID1 while RAID5 stays

[Ayman Altounji]

I need to upgrade a pl5500 with the following disk configuration
4x18,1GB in RAID1 and 9x18,1GB in RAID5.
Now I want to replace the 4 disks of raid1 to 6disk still in raid one.
So far so good, I remove all disks and put in the new ones, run smartstart and prepare the disks to be in raid1. Next I install a NT recovery and put a restore on it. In theory this is working fine. I've done it ceveral times. But this is the most critical server of the network. So I want to be able to perform a rollback (that's the reason why I'm keeping the 4 old disks). I did some testing in lab. And I can't find a straight forward solution to go back to the original configuration. I switched disks, but got an error that there were problems with the array; so I ran smartstart ->ARRAYconfig, en afterwards I lost my RAID5 disks. As you can imagine, I cannot afford this situation in production.
So does anyone have experience with this?

Thx
Bart