Most of the modern avionics have two pins for power input. One way is to stop brown outs is to hook a device like this to the second pins of the components you want to power for the start.

Another way is to have a second battery that can power everything or an essential bus that is isolated from the start circuit and main battery. I designed my own backup battery system that uses this method.

I don't know anything about Vertical Power, maybe someone who does can chime in. Maybe VP already has this feature built in.

Check out the document tab for the TCW device, it shows how to hook it up to multiple systems.