I recently received a comment on the blog from Steve (also a draft judge) inquiring about distance from the rear legs of the dog to the cart. He wrote that the guidelines online are vague about the distance so I wrote back to Steve. Unfortunately, I wrote back to the wrong Steve. Steve, if you're out there, this blog post is for you.
My email to the incorrect Steve:
My trainer said that there should be enough space for the dog to extend their rear legs while in cart, but not hit the cart. As a quick guideline, it should be an 18 inch ARC (not the direct points when standing) from the foot to the back of the cart. I'd have to put Mouse in cart to measure the distance from point to point instead of the arc. The length might also be different for each dog, given the height of the dog and the dog's hocks.
There's nothing inherently unsafe about having the cart much further away from the rear of the dog as long as the traces are snug. The problems you get when the shafts are too long and the cart is too far away is that it is difficult to maneuver, and the turning radius is much wider. The shorter the shafts, the easier it is to turn. However, if the shafts are too short or the dog was placed too far back (move the brakes forward to fix), then the dog's foot or hock would hit the bottom side of the cart.
I would not fail a team for having really long shafts as it isn't unsafe. It is a mechanical disadvantage that the team will have to work with that may cause them to fail. That's the handler's responsibility and choice to have longer shafts. However, if the shafts are long and the traces are not tight, I may fail the team depending on how dangerous I perceived the rig. I judged one particular trial in which almost every single team had really loose traces, even after I warned them of how dangerous it was (it also changes the point of pull). Anyways, one dog was almost pulled down a big hill when the shafts slid out of the shaft loops. It nearly gave me a heart attack seeing that happen.
I would also fail a team the dog's rear was too close to the cart, but I don't think I've ever seen that in practice or at trials. Dogs are usually too far with loose traces.