[Pat Fairbank]

Nope, there's no way to tell what frame is being sent, since it's a function of the master microprocessor, not the user.

However, you might have noticed that all 16 PWM outputs are also sent out the dashboard, so if haven't got any Victors hooked up to some of those, you can use them to pass extra bytes.

If you need even more bandwidth, you could probably set up some interlacing of your own (e.g. use one of the user bytes to describe what data is in the other five).