This is totally newb but I must get the expert advice. I have this frame and it does not have the braze on cable stop. I need to get the clamp on thingamabob. Are they pretty much all the same? I am guessing when you clamp it on tight enough to work the paint underneath will get a bit messed up and/or faded.
You can protect the paint somewhat with a strip of thin hard plastic, I've used a sheet of mylar that came as protective packaging on an LCD television screen. The clamp in the link probably won't mar the paint at all if it's fully cured or factory paint.