I had bought a tbw aluminum undershroud last year and ot held up pretty well, definitely scraped pretty hard in spots. 2 weeks ago it met a raised sewer plate going about 20 mph and a big piece of it broke off. Nothing wrong with the quality of it or anything like that just was too much for it. Well i was going to try the z1 undershroud to see if the fitment was any better but i lacked the $240 for it and i didn't like the idea of leaving it open underneath especially with it lowered. So i made own out of a hood of a 91 s10 blazer. I did save the front piece of the tbw that connects to the bumper because it wasn't damaged at all. Traced the front shape of the rear piece and cut to a square size, marked and drilled holes using the tbw like a template. I flipped it over to Trace the holes from the part that was broken off. Waiting to get a 3/8 16 tap tomorrow to finish installing it, one of the 10 mm bolts got torn off destroyed the threads on the subframe so i figured to retap with something a little stronger. Had some grade 8 self tapping bolts from work but i think i lost them somewhere. Anyway this is what i came up with. Drilled extra holes for drainage and heat dispersion. Steel is a little heavier than aluminum but the strength is something I'm willing to trade off. That and it was pretty much free.

 

The piece that broke off my tbw.

 

Nice
are you gonna put an oil filter access door in it?

I have the opposite problem, my front/bumper piece is mangled. They state its available separately, but guess what? Not!
so I found a used replacement and am gonna bend/cut up the larger portion into a rear diffuser/undrtray
kinda like you see is available for the sedans.

 

No, I'll just remove it entirely. This one actually fits better than the tbw, had to shove some things to get it to line up each time.

 

I have the Z1 cover and the squared edges of it scrape on certain speed bumps here in town. It's also mounted very well to the underside. Almost too well as I worry that it will tear something more expensive off if a situation like yours is encountered. When I first installed it, I swore that the front end of the car felt more rigid. Figured at the time it was just my imagination.

 

I think the 10mm bolts that mount it would go before anything serious. I know anything that impacts it from the front goes against the sway bar first, if i didn't have it I'd hate to see what my hotchkis sway bar would look like now.

 

This is my winter car too and it also keeps the salt out pretty well. Though we'll see how the steel holds up to it compared to the aluminum.

 

Well i got everything bolted up today, looks good to me.