you know what would be really cool is if you could figure out how to ram the batteries into the detector shaft. Design the battery pod to fit into the detector shaft. Wouldn't be that hard if you have access to the resources.
the further back the better.
You might even be able to figure out a way to run all the cables throught the shaft as well
You could also greatly reduce the weight by using carbon fiber tubing. Should save a few ounces at least