So is the derailleur mounting bolt too long?
If so, cut it a bit shorter.
Before getting the hacksaw/dremel out you'll need to protect the thread. You can do this with an axle locking nut - restores the thread when you remove it.
The bolt (on the hinge, that’s not the mount to the frame) is hitting the chain in the photo, but actually if that wasn’t in the way, the bit the bolt goes through hits it anyway, and I can’t trim that. Perhaps I can get a mounting arm that’s longer?
So is the derailleur mounting bolt too long?
If so, cut it a bit shorter.
Before getting the hacksaw/dremel out you'll need to protect the thread. You can do this with an axle locking nut - restores the thread when you remove it.