The print does not require any supports. I printed with PLA for modelling, but will print with PETG for the final rev. PLA should be fine if the transceiver never leaves your shack. PETG is going to be required if you plan on leaving it in a go bag or portable.
The end cap is snapping on for me. If it gets loose, I will use a drop of glue to hold it together. The lock washer and nut for the BNC included with the QDX will hold the board into the enclosure, negating the need for the end cap all together. Which may be a better solution for keeping the finals cool.
The author hasn't provided the model origin yet.