[daltore]

You don't have to have every module chained to two other modules. For the explanation, I'm going to use FL, FR, BL, and BR for front left, front right, back left and back right, so just a heads up.

If you have the opening in the front and the motor in the middle of the back, you have the motor directly chained to BL and BR. Then BL is chained to FL and BR is chained to FR. That's 4 segments of chain. FL and FR are not chained together, which leaves the entire front part of the robot between the wheels open, and you still get single-motor-steering crab drive.