[kach22i]

The problem is the air isn't going to go only where you want or decide it should go.

What's going to happen is the air on the sides will travel around this really sexy curve shape, the air above and below straight across.

It's going to take longer to go around (air at sides), the air on top will not be traveling at the same speed, there will be air pressure differences between each side and the top/bottom.

These pressure differences will cause air to be drawn to the low pressure areas, and as it does this it will be over distance which in turn causes a swirling or vortex.

The vortex is a funnel of twisting air which results in high drag once air flow further out from the body in motion contacts or interacts with it.

Your design sounds like an old soap box derby car, which I'm sure at the speed it operates at does okay as the vortexes are not too large or violent. However if you want to compete with the Velomobile, you are going to end up looking like the Velomobile.

I'd like to see a sketch or diagram of your design, the devil is in the details, and where your head is and it's treatment is rather important in the scheme of things.