Concept Mongoose 4WD articulated?

Here's a concept for a pair of Mongoose chassis with an articulated joint (not drawn or designed as of yet)
All wheel drive.
Question, what type of articulation would work best?
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Front/Rear like this:

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Some people liks this:
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But I could never figure out what good it does.

I'm thinking of a servo connection...
I don't think you like linear motors very much (they cost big money).
Tell me, if you need drawings of it...

EDIT: 1more question. What type of movement do you want? Do you want to be able to turn (like a car with a caravan) or something "silly" and "pointless" like on the images above?

Who says you even need a motorized linkage? I guess you could pull it off on something this small though.

It may get too long by the time you put a joint between them.

If the PCB on the gearbox is not in the way, mount the front of one to the back of the other.