Just a quick note to share what I've learned about JRR - you can move people about on the grid before the green lights without triggering the false-start system. Handy if you need gaps on the grid, as the REO packet doesn't allow them.
You do need to buffer the cars somewhere else first with an additional JRR though, as the JRR will allow them to spawn in an identical position as you work through the cars, and any slight movement will trigger a monster lag-hit type collision. I just use the co-ords of the pit start positions - move them all there to clear the grid, then all back to the grid in their correct positions.