MV- thanks, she really has a good head about things. I had looked a lot into blinders/open and I want her to work well in both, as you never know when something is going to go wrong and you need to use the other (she'll be a carriage horse, so mainly blindered, as there's a lot going on to distract her in an open bridle). From what I've heard, it's usually easier to start them open, and then transition to blinders, than visa-versa.
I can pull the cart up behind her, as if it were hooked, and just lead her while I pull the cart, but she has no respect for the shafts. When I asked her to turn, she just bends right into the shafts, which tips the cart right over (I used a smaller, dinky metal cart, I'd rather pay to replace that if she panics than the new one). I'm thinking about getting some wooden poles and strapping them to her, where shafts would run, so she learns she needs to keep her body straight in a turn, but does anyone else have any suggestions?