I 'thought' was able to cheaply fab up a front spoiler for my Dart. Just for kicks, but I found I got my butt kicked by 'geometry' here a bit in the progress.

I went to our local HomeDepot and grabbed a nice large cement bucket. These things here are made of very sturdy, but unbreakable plastic. Perfect for possible groundscraping once in a while I thought.

Once in the garage I started cutting the reinforced top edge and 4-5" down off it. Also made pie-cuts in the lip to straighten out the curvature.
But then I hit a geometric snag. Because of the taper of the bucket, the now 'straightened out' strip, was still curved along it's entire length when flattened out... Duh...
Also the curvature was the wrongway around for it to even remotely fit.
So I cut another strip, but this time from the bottom of the bucket and did a mockup on the car. Secured it with the center valance-bolt in the middle and a number of tie-raps towards the edges.
Not happy about how quickly the strip curves upwards behind the valance, I'm now looking for a 'real' spoiler.

Usually, my first attempt at making something from scratch is pretty much shoddy at best, so with that knowledge I always have better hopes for the second attempt...!