I saw that, and I think they have vents in it for that purpose.

 

With the price I have seen people paying for cold air intakes this is not a bad deal and it provides all that you are looking for. As for your gas tank I wouldn't worry so much. A pain in the ass to change your oil I presume.
I hope this helps.

Kami Speed - Beatrush UnderPanel- Fit - Beatrush, C-ONE, C-West, Fujitsubo, JDM OEM Parts for RSX DC5, Celica ZZT231, & More JDM.

•Fits 07-up Honda Fit stock bumpers and most after market bumpers
•Air turbulence is significantly reduced, producing a more stable ride at higher speeds and increasing down force by creating higher suction pressures between the panel and road.
•Engine temperatures are reduced and stabilized by removing heat from the engine compartment with specialized slits made to draw out hot air while the vehicle is in motion. This is successfully achieved during the creation of down force, as this negative pressure sucks out the heat and is then swooped out by colder air moving underneath.
•Provides greater protection under the engine than stock plastic panels during heavy track or circuit racing competitions.

 

You might also try contacting the folks at Dieselgeek they make skid-plates for VWs and might be able to help you in your search, or maybe even make one for the Fit for you. For an arm and a leg of course!

 

I just updated the Beatrush Underpanel thread with a bunch of pictures of my install.

The panel is aluminum, about 1/8" thick. Quite sturdy considering what it was meant to do, which is to divert air. It covers the entire underside back to the crossmember. It will certainly keep gravel-sized stuff from bouncing up into the engine/drivetrain bay, even big gravel. But if you are physically crashing onto rocks with the bottom of your car you may want something more substantial -- like a Jeep!

 

beatrush makes an UNDERPANEL not a SKIDPLATE it's like comparing a warm down filled vest vs a bullet proof vest, the down vest will prevent some branches and twigs from bruising/scratching u and will soften some blows but like the underpanel it was not design to for impacts and the car bottoming out and skidding on the road surface (look at real rally/offroad skidplates and u will see that they are double the thickness of the underpanel)
the underpanel is nice though

 

I need to replace the plastic undercarriage. Would you fabricate one and weld one to sell?

 

It would be cheaper for you to get it here.
BEATRUSH Aluminum UnderPanel 2006-2008 Fit

If you are serious in looking into something rather heavy duty I could build one.

 

Check the gorram dates on these threads!