I think the first pic is more doable because you aren't messing with your fwd visibility. Going up is a brilliant idea since you aren't increasing your road footprint, just A, but in return you get a smoother airflow around the whole body. It's worth a 5% increase in A if you lose more than .05 Cd (and I can prove it mathematically
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I thnk you would want more of a dome shape on top, like a turtle shell. Less material (weight) and A.
I looked at diesel Rabbits on ebay and good ones are going for over $3K! /OT
I worked with a guy that has a vacuum table that could form something like that, but I have the feeling it would be many months of lunches.