Chain Bracelet

The challenge I tried to meet with this design is to make a design that could chain together but that would not come apart if you randomly shook and flexed it.
The two different pieces will only go together (or come apart) in one particular orientation. In this way it is almost a puzzle. Not sure if I need to post now to do it.
The full size print is (I think) big enough that a child can't choke on it. I am not really sure what the official dimensions should be, does anyone know?
The smaller print I printed at 50% scale which makes it 1/8 the size. Seems to be about right for a small child. With PLA at 50% scale it seems to be easily broken right down the middle. I will have to try it a bit larger.

It is not really configurable since the dimensions are fairly dependent on each other. I have included the source file so that you can try playing with it if you want.

The bars across the back are actually there for strength, but I think they look ok. I thought of making them a cust