I agree with Mattman, the prussik should be your controlled failure point. if you break the rope or a carabiner/pully you will have a large mass flying through the air and it could damage something or someone. Always make sure you dampen the system, what ever the set up, clip a pfd for a dry bag to the load stand of the rope so if it does break that will slow it down.
Full disclosure: I suck at spelling and grammar, so if you find an error, great! Keep it to your self I don't care!