Well, my trade show weekend was a fantastic gateway-activity for driving, hanging out with the draft show people was a blast, and they helped me out a lot. I got some advice on how to keep working toward putting my filly to cart, and surprisingly the consensus was to do the next few steps myself, then go seek a trainer.
While the driving folk were very safety-conscious, and full of warnings and cautions, they were also very encouraging.
I have decided that once I get through the next few steps, I am going to use a Forecart to break this mare to a cart. I have a collar and hames harness that fits her well, but I can't seem to get a handle on sizing the cart...I am reading conflicting information. It seems sensible to me that the center of the axle and the hames/trace buckle should scribe a line (axle draft) and also stands to reason that the singletree attaches to the traces along that line (traces along ideal line of draft.) In many photos of the Pioneer Forecarts, the traces aren't connected, or else are slack...but I can't really tell...and in other photos, the traces are running behind the shafts, which would seem to eliminate axle draft. Some forecarts have the single tree mounted above the shafts though? How does that work? How much rise should there be in the shafts? Does that matter in a vehicle of this type? https://www.mydrafthorse.com/cfwebst...GO-TRAY-00.jpg
This mare is heavy and drafty, but not especially tall at 16.2hh, and VERY short-bodied (front to back) so I'm not confident that a "draft sized" forecart will necessarily be the best balanced. She's built a lot like a Haflinger, but quite a bit taller than most of them, with longer legs.
THIS cart seems to show the axle draft, but it has the singletree mounted lower than some, and the shafts "look" a bit low...I was thinking you wanted those to sit higher on the horse's body, but probably not have too much rise.