Yes, I have EVP too :)
The settings I'm getting stuck the most are about the clutch on manual, and automatic gear changing for automatic, I still cannot find perfect values for these heavy vehicles to mimic real ones. It would be great having a sample with a Citaro or MAN bus, for example (very popular on Europe).
In Brazil we have lots of manual buses, there's something in clutch that is not great here too.
Talking about simple boxes or placeholders... I was using box colliders since NotifyCollidersChanged() apparently had a bug in the version that I'm using (one of the latest with source on Professional license). I got lots of runtime errors if I disable or add new colliders (at EnableCollidersRaycast and DisableCollidersRaycast).
After your comment about "placeholder models being EVIL" I decided to put a try...catch inside the loop on that functions in VehicleBase, now it seems that I can finally use MeshCollider with VPP (it is loaded at runtime as user vehicle mod). This will improve behaviour a lot on certain terrains, since on the back part of the bus the body border is more elevated than on the middle.