Great news! Starting v7.1, RaceChrono allows adjusting the timing data from CAN and OBD devices relative to the GPS data, and even can do that automatically.
As an example, here's T6 at Laguna Seca:
Here's the data log from that lap, after aligning GPS and CAN data:
Purple line: GPS speed
Cyan line: Speed as reported on the CAN bus (from rear wheels)
Green line: Accelerator
Orange line: Brake pedal
Now that GPS and CAN data is aligned in time, you can see that the tire "slip" between 3s and 5.5s.
It's very clear that the GPS data is wrong when going under a bridge.