We did look at trying out a real-time kernel, but decided that if we could achieve tolerable latencies with a stock kernel + tunings, then that would be prefera

We did look at trying out a real-time kernel, but decided that if we could achieve tolerable latencies with a stock kernel + tunings, then that would be preferable. When ~2us jitter becomes an issue, we'll revisit our options, and no doubt share our findings. Thanks for the link to Xenomai, I hadn't come across it before.