Hey is there a kilted metallurgist or structural engineer in the house?
As a matter of fact, yes, I'm a licensed Professional Engineer in structural engineering.

Hmm, the yield strength of brass is at least 18KSI. Assuming that the ring is about a 3/16" diameter brass rod, it has a section modulus of S=0.000647 inches cubed. Thus, the moment strength is approximately 11.6 in-lbs. If the brass ring stands off the back of the cantle by about 1/4", then technically the clip should be able to pull about 46 lbs laterally on the top of the brass ring before it reaches a permanently yielded failure mode (i.e. permanently bends the ring at the root where it is attached to the cantle).

Of course, cyclical stress analysis should be done too, in order to check long-term fatigue issues, but let's not go overboard!

Honestly, Matt is right. Regular use shouldn't bend it with it just clipped to the top. But you may find wear marks and scratches from the harder metal of the clip marring the softer brass over time.