I am going to experiment with modifying a whistle buckle by carefully grinding off a bit of the outer edges of the buckle's male side 'prongs'. The 'hook' at these spots is what engages with the female side of the buckle, and I think if you shaved a bit off of those hook edges you could make the buckle release when overly loaded.
That's exactly the same way I make breakaway buckles for my badge lanyards. I shave the hooks back to about a 30 degree ramp, and the buckle separates with about 3 lbs of force.