What I would do with that YRX-12 WE that you just bought from Mr. Shookie, would be to put a 12LR chassis, lower motor pod plate and rear chassis cross brace under it. Yokomo does not make a thick chassis. While the black Yokomo chassis does move the batteries in, it is still a thin chassis, which does not lend itself well for carpet racing. In the winter for racing on carpet, just throw the 12L4 chassis pieces under the Yokomo. In the summer, when you go outdoors, put the YRX-12WE chassis pieces under the rest of the Yokomo kit and you will have the best of both worlds!