I briefly checked the OpenVizsla packet format and noticed that there is:
HF0_TRUNC = 0x08, // Clipped due to packet length (> 800 bytes)

Then I noticed that this seems to originate from the software/fpga/ov3/ovhw/whacker/producer.py which has the MAX_PACKET_SIZE = 800.

Is there any actual reason why there is such an arbitrary limit set? Why not make it 1 + 1024 + 2 = 1027 (PID + Data payload + CRC-16) to match the USB 2.0 high speed maximum for interrupt and isochronous transfers?