Under ideal conditions, you can go 5x AV Pro 2 storage hubs deep in the chain. You can also connect a USB device, such as CalDigit Tuff or Apple SuperDrive, to the Hub ports on the 5th AV Pro 2. Additional USB-A to USB-C or USB-A to USB-micro B cables are required to connect to multiple AV Pro 2s in a chain.
Below is the setup showing the entire USB Hub chain including 5x AV Pro 2s, 1x Tuff and 1x SuperDrive.