[MrForbes]

The wood chassis by itself seems to be plenty strong and stiff, and like I said before it took us an hour to build it, and cost $20 for the materials.

If you think it could use improvement, I suggest you build one yourself, and see where the weaknesses are, and let us know how to make it better! After all, it only costs $20 and an hour of labor. (yes, I'm making a big assumption, that you have the machinery necessary to build it....but that is mostly the same machinery that has been required to build bumpers the past two years)