Butt in the dirt, your harness is also hooked up incorrectly. It is hard to see but I think I am correct in saying you breeching straps are attached to the saddle, belly band, shaft loop area. The breeching straps should be attached to the shafts at the foolman's loops,( the hardware under the shafts between the crossbar and shaft tips). It looks like you have attached your girth wrap straps (the outer girth that comes up wraps around the shafts and buckles back to itself) to the footmans loops, I wrap the wrap straps around the shafts once infront of the shaft loops (where the shafts go through the harness to hold them up) and once behind the shaft loops. That holds them together. I had noticed in your other thread that they had separated in a few photos, that area (wrap staps & shaft loops) should not move back and forth on the shafts at all. Yours look like they should be placed about 6-7" in front of the footman's loops.
When I harness I like my horse very snug in the harness there is only about 3-4" of movement when you move the cart forwards and backwards. That way the vehicle does not BANG into them. When the horse is troting its rump comes in full contact with the breeching, not tight but touching. Also when your horse first walks off there is not a lot of daylight between horse and breeching, when horse is standing can put a fist between horse and breeching not more.
I hope you can understand my explanations. Your horse is great.