So here is an initial assembly idea of what the test bed will look like. The front bay will be for seating a battery, the finished test shell would likely have venting for batteries, maybe some kind of hexagonal pattern at the bottom. The idea of keeping it as sealed as possible is to prevent sand ingress into the motors and electronics. 

The rear component is a hinge design to actuate the tail, Tortuga when wanting to carve into the sand will actuate its tail downwards at a set angle and drag it behind it, producing the desired line. Not shown: 

Servo to actuate the tail

Nose wheel steering servo

Batteries

ESP32 or Raspberry Pi 0w