I've got mine bolted on as your picture shows with a single bolt and angled down towards the ground.

I fastened them on with 3/8" quick links instead of the crush style chain links. The 3/8" ones are a little too big as the nut part  you turn to close the link will work and get stuck in the hole of the drag arm. Does not hurt anything but I'm going to switch them out to 5/16" versions like these. They are enough small er they should pass through the hole instead of getting stuck.

I have not had any issues with the chains getting caught or flipping up on curvetines or closing wheel down pressure handle. but I plant between old corn rows and ground speed is not all that fast.

I am also running the Dawn half rate closing wheel spring and leave the tension in the first notch.

You mentioned the "M style" Dawns what are those ?

Mine bolt directly to the JD tailpiece studs but I am told these style wheels are no longer available ? Now I must either convert to a newer style tailpiece where I lose the adjustability of the tracking with the eccentric cams or I have to buy a bolt on hub  that the newer style wheels bolt to.

Probably need to update my Dawn wheels as mine are starting to get worn down some but don't like the idea of having to buy hub and wheel this time around. These have been trouble free but I think they have worn a little faster than I would have liked to see.

Maybe someone from Dawn can comment on this situation with 7200 planters and comment f newer style are wearing any better than what I have.