Since you are having trouble with her turning around, although getting better, she might revert at the next step; I would defiantly do a couple more steps before a drag. You don't want her to spin with the traces connected to a drag, and get her legs caught.
I would ground driver her with you pulling something noisy. I use a bucket with some rocks in it, or a shovel. I put it on a rope and hold the rope in my hand, so I can drop if necessary. This is good to get horses used to noise behind them; the more noise the better, then when the relatively quiet cart is behind them it is no problem.
You guys look great, but please get in the habit of putting your extra leather through the keepers. It is a safety measure and it keeps your harness supple and prevents the keepers from shrinking.
Another step I will try and have this afternoon.
The best time to plant a tree was 20 years ago, the second best time is today.