Does anyone have advice on joining a new switch stack to an existing to extend customer ports?

The place I work at has a setup pictured as follows on the left of the diagram.

https://i.imgur.com/90CijiM.png

Hoping to add a new stack in to extend the amount of copper ports/customer ports and not sure of the best approach. Current stack is a ring topology using Ruckus/Brocade campus switches and supports a maximum of 12 in the stack hence the reason for a new stack being created.

Any advice on how best to structure this moving forward would be great. Thank you.