Sounds like you have the file system changes well in hand.
As for rearranging the disks, perhaps the easiest way to present it is with a before and after list.
Current:
Parity1 - SN
Data1 - SN
Desired end state:
Parity1 - SN
Parity2 - SN
Data1 - SN
etc.
When you map out what drives you want to add vs. remove vs. move to new slots, we can give you 2 paths, safest and quickest.
Do you have full backups of anything important? Mass reconfigurations like this are a really easy way to accidentally lose data.
Also, when was your last parity check with zero errors, and are all the drives SMART tested good?