I'm posting pictures of my ECO4's factory fitted belly pans which were fitted to improve FE only just in case a few of you would be interested in seeing how a car company would shape/fit it. I really hope these will be useful for you! For more pictures, or more specific ones, just let me know and I'll be happy to take them. It's interesting to see that the engine cover has holes in it, I guess to allow some air in for cooling.
Pic 1 - the engine cover
Pic 2 - Another view of the engine cover
Pic 3 - The back of the engine cover. Bit hard to see here, sorry.
Pic 4 - Rear pan - I think to cover the fuel tank
Pic 5 - Back view of the rear pan. Not a lot to see.