[Poodwaddle]

As a new (and amateur) student of aerodynamics I would like some feedback on a concept I have banging around in my head. I want to travel and camp around America for 6 months to a year. I have a family so I can't exactly drive a metro, but I still want to maximize my MPG. Driving an RV is out. Those boats get 5-8 MPG. I have build and welding experience to the months of fabricating would not be difficult. I am debating buying a 2003 or older Ford cargo van with the 7.3 diesel, cutting down the cargo box and welding up a pivoting roof that would fold down to form a teardrop-ish shape. The construction details are already pretty well formulated, but what I am wondering is whether it is worth the trouble. Would the semi-teardrop give enough benefit to warrant the extra effort and cost of the folding roof? The pivoting roof would have to be framed in aluminum and the entire construction would be much more complex and more expensive than a solid build. I figure that a 7.3 diesel in a typical Ford van gets 18ish MPG to start with when driven by a typical lead-foot truck driver. Clearly I can improve on this with some good driving habits, but more important to me is estimating how much the drop roof will improve the fuel economy. It has to be better than a 5 MPG improvement to pay for the extra cost of construction. As you can tell, the inspiration is a gypsy caravan. I haven't bothered yet to draw the interior, except a few scratchings on restaurant napkins. Yes, I realize that the shape is not a true teardrop, but aesthetics and livability do have to be factored in as well. Give me your opinions and ideas. What would my MPG potential be? What other ideas can you suggest to improve efficiency?