Here's the idea---
I've been piddling around with sheet metal lately and have become pretty good at shaping it. So, I was looking under my car this morning and I am satisfied that I can completely cover the undercarriage with sheet metal.

Questions:

1. Will this sheet metal hold up to high speeds?
(I'm afraid it may flex too much and affect performance.)

2. Is there anything besides sheet metal I can use?
(Not looking to spend a fortune on CF either)

3. What should I leave uncovered?
(Obviously, I need to leave the exhaust open and under some of the engine bay to allow the trapped air to escape)

4. Will this even help me at high speed (considering I do a clean install)
(I'm looking to make my car more stable at high speed, I've seen rear diffusers and front under panels)

Here's how:

Front-
Just like Mugen or etc... Extending from the tip of the bumper to the oil filter. (That how far it looks to go back anyways)

Mid/Back-
From the back of the engine bay--from side to side (accounting for the open exhaust area)--to the rear bumper

I'm hungover. So, excuse me If I am not clear enough. Thanks!

 

I don't think you will really see much gains in relation to the work that would be involved.

You will need to be able to remove or have access to the diff, oil and tranny to name a few.