An appropriate way to add extra capacity into an existing aggregate?

I need to add 2x24 SAS shelve into an existing aggregate, and it's current layout as shown in the attachment.

I am going to create two more raid groups with the same size of 22 disks as rg4 and rg5 in the same aggr. However, my questions is, should I also need to use extra 2 disks into rg3 to make it up as full raid group? would that cause hot spot on these two disks? ontap 8.3.2 cdot.

Thank you!