That LiPo isn't going to like those motors when they're firing on all cylinders. It can safely put out just 44amps, which if you're looking at stall currents of up to 100a per motor, is very underrated. By rule you need a fuse in there, it has to be quite a bit lower than the burst current of the LiPo, say 50a, you're likely to blow that when you're trying to push something.

This weighs virtually nothing if weight is an issue and I'd argue easily worth the 20 quid. Even if the numbers advertised are a bit wishful it's going to have a burst rating within the stall current of the motors combined: http://www.hobbyking.com/hobbyking/stor ... ouse_.html

If nothing else it protects your investment, we can all imagine what a LiPo failure could do to a wooden robot.