The shape of the vehicle will impact a lot of variables in the future. Right away, it will have a significant effect on your Area value.

This is seen on catamaran and trimeran ships, on multi-engine airplanes (especially of World War II vintage), and in many of the more fanciful science-fiction spacecraft. It imparts an increase in stability and maneuverability, but at the cost of increased surface area. This will result in a greater percentage of the vehicle's mass being given over to its hull and armour.

If your vehicle falls in this category, multiply its Area value by 1.2.

If your vehicle is a submarine, it will need a pressure hull. Multiply its Area by 1.16 to account for that hull. Also, be prepared to spend some mass on that hull in the next step.

Streamlining will improve the speed of many sorts of vehicles, but at the cost of increased Area.

No Streamlining is the base; there is no change in Area.

Mild Streamlining is typical of sports cars, most ships (anything more streamlined than a raft or barge), or propellor-driven airplanes.

Moderate Streamlining is commonly found on supercars, submarines, or sub-sonic jet aircraft.

Good Streamlining is common on supersonic jet aircraft.

Excellent Streamlining is normally only found on missiles, rockets or the fastest of airplanes.