The beginning of the belly
 

I have finally, four years after I bought it - and 46 months after I discovered the thing was missing - replaced the the belly pan under the engine in my HCH1.

Material is coroplast from Home Depot. About $14 per sheet. Don't flame me for paying, I have just enough social anxiety that even thinking about calling campaign offices for permission to take abandoned signs gives me hives.

I'm not worried about sagging; I put the corrugations crossways on the car to provide a bit more rigidity that way, and a gentle curve where the forward edge rises to meet the existing under-bumper tray stiffens things up in that direction.

I provided a generously-sized trapdoor for access to the oil filter and drain plug. I'm pretty sure that a quickie-change place probably tore the old one off and discarded it; that appears to be a recurring theme with people who complain that their undertrays are gone. I use a Walmart near me, but I know the guys that work on my car.

I was able to use the existing mounting points for the original tray; I bought a bulk bag of 50 push-through trim anchors specifically for this project and extending belly panning aft.

Pictures are forthcoming, as soon as I can build a link to them.

[edit] Pix!
http://i.imgur.com/0TEiTqgh.jpg
The approximate size of the sheet I needed to install. The corners needed trimming but overall about 35x27" (90 x 68.5 cm)

http://i.imgur.com/pCAG7Bnh.jpg
The yawning chasm where the undertray should have been.

http://i.imgur.com/w5NA7D9h.jpg
The new tray in place. The trailing edge of the bumper's undertray had been missing its buttons for a long time too, so everything was quite droopy and sad-looking under there. This has neatened things up a lot.

http://i.imgur.com/0VwTgn5h.jpg
The maintenance hatch. For anything more involved than oil changes, the whole thing will have to come down.

Pictures aren't working for me right now, but luckily I can use my imagination. I don't blame you on not taking the signs, back when I did similar on my old car I just went and bought home depot coroplast as well. Glad to see some progress from a fellow east Tennessee member.

Looks great. Let us know how much of an improvement it makes, please.

Looks a whole lot cleaner than mine! I like that triangle wedge idea to hold up the maintenance hatch. I just take the whole engine tray off mine for oil changes. If I were to try to make a hatch for mine, it would weaken the already weak area that the drain plug is nearby. I think the oil filter doesn't need the pan dropped.

Orientation
 

Wouldn't it be better if the hatch opened the other direction? The way it is facing now it could get blown open while driving down the road correct? Or is it attach good enough not to worry about it?

RE: weakness caused by the hatch - I reinforced the edges of the hatch opening with an extra layer of material, which also provided a flange to stop the hatch. I've had the car up to 70 several times since installation, and that's about as fast as I ever go. No buzz or loosening yet.

RE: opening direction - the hinge edge is the leading edge. I can't get the car very high up, so the pictures can't provide a lot of context.