6xAA battery mount for 2 wheel robot chassis

I purchased a cheap 2-wheeled robot chassis which came with a single 4xAA battery holder. I wanted to use rechargeable batteries and power both the motor and electronics from these so I decided to use 6xAA batteries (7.2V). I designed this mount to hold a 3xAA holder on each side directly above the passive wheel, providing a counter-balance for components on the other end of the chassis.

The mount is designed to be fitted using short PC chassis screws although cut-down flat head self-tappin