From the looks of them you'll probably have to pry them down as they've gone over-center. I'll guess less than an inch longer is all that's needed. They only need to be long enough that the shackle will have a slight angle down from horizontal when the main leaf is dead flat.
Or you could leave them alone and add a thin urethane bump-stop to the bottom of the frame where the shackle eyelet is making contact. Choose the stop to be tall enough that the shackle can't go over-center even with the stop slightly compressed. These won't take the place of a normal bump-stop, they only serve to keep the shackles from going over-center.
To keep the spring close to the frame you could drill through the frame or weld on top of the frame with a longer shackle that would not lift the trailer more. Or go with a slider shackle like I used.
Energy Suspension parts from Summit.Thanks ntsqd,
I am going to make my own shackles. Any suggestions on where to source the bump stops?