I heard from a friend that in some cars you can simply flip the springs upside down and it will, in effect, lower the car an unknown amount. He said something about the spring compresses differently or whatever.

This true? Seems a bit odd to me, but hey...ya never know!

 

Also, 3rd-gen Protege rear springs are tapered. They can't be installed upside down.

 

Nope, at least not on a 3rd gen...The rear springs taper to a smaller diameter on the back, so they won't sit right on the perch's upside down. On the front the top portion of the spring is flat, and so is the top hat, and the bottom sort of spirals into a rubber retainer (there is also rubber on the top perch), so they also would not sit properly. Removing the rubber pieces will allow the springs to shift during driving, and possibly pop out of the perches all together, which will lower your car but not in a good way....