Fortigate HA cluster and total count of supported switches

Hi ALL

I have question , and maybe someone from Fortinet can answer.

I have HA FG300E ( 2 devices) but we need to install more  switches then one unit can support. And the question is how Cluster manage total supported devices. Is it still 72 or is 2x72 and switches can be spited between each FG.

How it's look like if we enable VDOMs ?

Thanks for any clarification .