This only works for increasing weight, so you would have to use something lightweight like a Miata. The problem with this is that a Miata won't be able to take

This only works for increasing weight, so you would have to use something lightweight like a Miata. The problem with this is that a Miata won't be able to take 600 whp. If you throw too much power into a car you'll just warp the frame. To some extent you can reinforce the frame, but there is still a limit. Regardless, adding weights to the car is going to destroy the car's center of gravity which will really mess up handling. You can test this with any car, put 100 lbs in your trunk and drive it around. It's very noticeable.