I honestly don't know if I still have the reference pic I used for the rigging, but here's a shot of the modeling I'm doing where the rigging fits over the tail. I'll see if I can find the reference pic.I'm not sure what you mean by reins fitting over the tail, do you have an image of what you mean? the image above looks right for the reins to me (except the reins should be a longer to fit in the drivers hands)
I can pop down to the farm one morning when they have the horses out and grab a bunch of photos, their everyday working harness has no crupper. It is pair harness, though, not singles, so it's not designed for shafts.I posted it mainly because its one of the few back ends I've seen that doesn't have a crupper which might help Earl if he wanted to get rid of the cupper if its going to be too hard to rig.