One circular saw blade each side works fine, even the thin ones designed for cordless circular saws, as long as you have most of the weight on them.
And if you have most of the weight on them, you of course need long wheely bars out the back to stop it flipping over (long wheely bars are much better than short ones, coz they take less weight off the drive wheels when they touch the ground).
see http://www.slowcarclub.com/santapod-07/drag-bike.jpg