How to double the bandwith with 2 HD1 Pro and one cable

I have a customer that wants to “daisychain” 2 HDmodems into one network connection, and use both modems to double the bandwidth.
Is this possible, and if so, how to configure?

Sure. Cable both HD1 Domes back to a Peplink Switch.
Set Dome 1 LAN to present on a VLAN to the switch (tagged only).
Add virtual WAN to Dome 2 and tell it to use the same VLAN you set on Dome 1.
Now Dome 2 can use two cellular WANs. Speedfusion will work, load balancing etc.

Would you happen to know if this design will work with 2 HD1 Domes both using a sim injector? Since the switch in the sim injector is unmanaged, it seems like the 2nd dome would not see the injector.

Don’t really want to purchase a vWAN license to find out this doesn’t work. Thanks for any insight you might have.