Got my bumper back from Josh at Exotic Car Specialties a few days ago (after a deer decided it needed some modification). Everything looks great, but I'm tired of having to touch-up the underside of the black bumper every time I enter a steep driveway, road intersection, or parking lot. So, I came up with a cheap, relatively simple solution.
Went to Lowe's and bought 3 pieces of 3 foot long 1/8" thick 2" wide mild steel flat stock, about 20 1/4" X 1" long carriage bolts (you'll need a few extra bolts) along with nuts/washers, and a can of black spray paint (or a color that's a close match to your car). Total cost, about $30.
The bumper was off of the car, so the job was a little easier, but it could be done while it's on the car as long as you've got an extra set of hands and you'll have to remove the access covers behind/under the bumpers. I also put masking tape on the bottom and lip of the bumper to prevent scratches and keep my Sharpie marks off of the paint.
Place the flat steel on the bottom of the bumper (I used one piece for each half and then cut the remaining piece down to a short enough size to do the sides) and, using a fine tipped permanent marker, trace the curve of the bumper and mark where the ends meet so you'll be able to cut and butt them up later. I used a metal band saw to cut my lines then a handheld grinder and finally a wire wheel to clean everything up, but you can also just use a grinder (about $50 at Lowes) to hack away at it. Then, using a grinder, put a bevel or radius on the front edge of the metal so it won't catch on pavement and rip the bottom of your bumper off. Once everything is fitted/cleaned up, hold them up to your bumper again and mark where your bolts will go, keeping in mind that you'll have to be able to access the backside to tighten the nuts. I used 4 on each side of the front and 2 bolts on each side-piece. To make your square holes for the carriage bolts you can either use (or hire someone to use) a press to pop 5/16 square holes into the steel, or(the cheap way) drill a 1/4" hole for each bolt mark, then, take a hammer and pound the crap out of one of your extra bolts into the hole. This is how I did it and it worked fine. Each extra bolt was good for about 4 holes before the corners wore out. Then tap them out from the other side and clean up the bulge with your grinder. Use the metal as a template and drill 1/4" holes in the bottom lip of the bumper (can be easily filled later if you change your mind). Paint the metal and bolt it on. Hardly noticeable unless you're really low and looking for it and it should (hopefully) keep the road rash off of your $7000 bumper.
I'll post a pic or two soon.

Sounds interesting. Pictures would be of great help, although isn't this something that can't be seen unless under the car?

nice, let's see it!

it's great to fabricate something functional isn't it... good job

Not sure if this will work. This is a view of the bumper off the car with the protective plates and bolts mocked up, but not yet tightened down. The second pic is a profile view of the plate and bolt. This can't really be seen unless you're under the car. If you're a Diablo fanatic, and know what you're looking for, you can spot it rather easily. Definitely worth it to prevent slowly leaving little bits of Diablo dust all over town. Now....... time to fabricate a brush guard for the front that'll hold up to a 200lb doe.

http://s1071.beta.photobucket.com/us...ghini%20bumper

Looks good. Although It looks like it's another 3/8' closer to the ground If I had the bumper off I'd probably attempt something, maybe some 18 gauge sheet metal and elevator type bolts which have no head.

I've seen 1/4" plexiglass, attached to bumper by 3M double side tape, so no drilling required, just hold plexiglass against bumper, mark, cut and double side tape, planning on do that myself when i take my car off hibernation.

Rayman, I like that idea. Drill a little coutersink into the steel and run some allen bolts flush with the metal. I have all winter (and should be able to scratch up another $40). Maybe I'll redo. This time, I'll make a pattern/template and take more pics. Maybe put up a DIY sticky. I also like the plexi idea, but with the amount of time my nose spends on the ground, I think I'd end up leaving it somewhere.

Great idea, you could also use 3/16 aluminum.

Abs plastic or vinyl would probly be better than alum since you want something that can take the scraping and some of the bump.

Great job! Looks good! There are some good ideas here! The plexiglass idea is a nice, quick and easy solution.........I like that one! I might make a trip to the hardware store today!