Before you do anything, start with setting up your alignment. From there you can do what you want for a shape.
The car is far from 5 oz, so no need to remove wood just to allow weight on the back end. Build a shape you like and add the weight on the back end to get to 5 oz. Only mistake would be to not have the rear wheels as high on the hill as possible.
Those rules should bring some pretty competitive cars. FYI, I've got one of those aluminum blocks if you guys decide to go for it!
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