Best practice to manage different switch-models (topology)

Hi,

in our main-department we are using a Fortigate 500E as main Firewall and Switch-Controller and several FortiSwitch 224E, which are connected via Fortilink in a ring-topology. So far so good...

Now we got some new Fortiswitch 448D, which we would like to use as a kind of Backbone.

The 224E have only 1GBit SFP-Ports, which are currently used for the Fortilink-Ring.

The new 448D and our FG500E have also 10GBit SFP+ Ports, so we want to use them, of course.

How do I manage this? Is the only option to integrate the 448D into the existing ring and switch from 10GBit to 1GBit within the ring? Does that even make sense?

According to the documentation, there can only be one Fortilink. But can I make one ring of 448D, connected to the Fortigate with 10GBit, and another ring of 224E, connected to the 448D?

Help would really be appreciated.

greetings,

Boris