Wow - that is some nice work on the checkpoints, then! (And the car flipping)
Pointing the arrow to the center of the volume should work fine. I mean it's got to point somewhere, right? ;)
The problem I had arose from the fact I could drive around the checkpoint, to the point it would be briefly directing me backwards, or sideways. Easy solution would be to make a rule for level designers - always make sure the collision volume for the checkpoints covers the full width of the track and slightly more than one car-length thick to prevent this.
Viewing post in Rambling Roads jam comments
well, yes and no.
as i've got it currently, every checkpoint does span the entire width of the road, often spanning into the rockface as well, but what i'll do different next time is have them point a bit beyond the checkpoint, or have the collision volumes be a bit thicker, so it get's triggered further before the center of the checkpoint. So that it doesn't get the chance to point backwards before it updates to point towards the next checkpoint.