i had this exact solution but earth was further away and arm 2 was 2 arms. Then i realised the 2 arms could be combined and literally improved my metric by a quarter.

20R. This idea can get you to 16R if you can geometry to work out such that the hexarm outputs instead of overloading the piston.

The silly stolen input saves 2 latency. it'd be very funny if that ends up mattering.