What size USB drives are required to hold new firmware? It looks like the firmware files are only 400-500MB, but usually they expect more space when you write them and they boot into a filesystem?
Replying to myself: my Z1+ came with a 8GB stick, and I've successfully flashed 2 different 16GB sticks with 1030 and 1105 firmware. 32GB and 128GB sticks both passed the flashing, but neither booted. (32GB would boot far enough to ping, but with no web UI... 128GB only showed red-light-no-boot)