I've been running some v5 boards as a test for a while now, and I've had a couple of digits on different displays begin to fail (the failure mode is they start to be markedly dimmer than the rest). The only reasonable explanation is that I'm over-driving them, so that means the Vf must be reduced slightly so that the displays are more reliable.

Fortunately, the store inventory of v3.1 boards is still holding up, so there's time to repeat the experiment with a different feedback divider on the LED Vf buck converter.