This is a remix of @geerlingguy's Raspberry Pi Pico GPS minirack mount, resized for a 6-inch rack. I had to rotate the raspberry pi mount to have enough clearance for the power connection to the pi. The only drawback should be the lack of a window to easily see the status lights on the pi, but otherwise the strength should be okay.

Supports shouldn't be necessary. The only overhangs are the two “tabs” that retain the pi, but they're small enough that they shouldn't have a problem printing without supports.