I think the tunnel may also give more structural strength than an entirely flat floor would. It is carbon fiber all right.
On the whole this incarnation looks much more solid, separate doors instead of a flimsy double sized wing door and no B pillar.
I like what they did to the back... fold the lower part of the sides in to reduce the wake, rather than a cone tail.
Don't think that is particularly safe for road use though, wouldn't like to run into that sharp rear edge.
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gmeter or 0.13 Mmile.
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For education go to people unlike yourself.