This is amazing. I hope it succeeds. If I had any use for a truck I'd be lining up to buy one. They make one in a compact sedan or hatchback form factor and I am in. Heck, even better a subcompact.
I compared the dimensions of the Slate with my '06 Pontiac Vibe hatchback, and it's only a few inches longer. I suspect the Slate + Fastback kit will be pretty close to a hatchback in size and function.