Discussions are always better with pictures!
The Pi 4 inside of a Sixfab project enclosure, wearing its modem hat, and connected to a 12 volt test battery:
The Pi 3b+ in a Canakit case, with GPS and 3 USB to Victron cables connected:
Size comparison. Even though the Pi 3 & 4 have identical footprints, the Sixfab box has room for the 5 volt, 3 amp power converter, two cellular antennas, the hat & modem, and a cooling fan! It is a well designed system.
With those blinky LED lights and transparent cases, these Pi’s will be installed hidden inside a compartment, so as not to keep us awake at night. The Sixfab hotspot can use larger antennas (external) if need be. I will have to test the reception inside the compartment using the stock antennas. Cell reception on our phones is usually not possible inside the trailer if the reception level outdoors is only one bar, probably due to the aluminum skin. Hopefully the Sixfab hotspot will be better at bringing in signal than our phones.