I'm going to make some custom splash guards this weekend for my HHR. I'm going to design them so that they will prevent any debris from being thrown up from the front wheels onto the back of the vehicle. I have done this before on my other toy, my Toyota X-Runner truck, which can suffer from the same issues. They don't look ghetto and no one thinks they are homemade. The flaps have to be cut low enough so that debris is prevented from reaching the back, and I don't think the factory ones are going to be low enough. See pic below which shows my X-Runner flaps. If you all want a write up with pics and dimensions, I'll be glad to post.

 

They are pretty low. You don't have clerance issuse with them?

 

No, not on the X-Runner because it is a "performance" truck and has stiff shocks. The HHR is going to require flaps that are higher, yes, but I want to also design the length below the frame so that it will prevent almost all debris from being thrown back. I think I can do that.

 

Well good luck and post some pics when done.
Sorry I don't have the dimensions. Some one here should.

 

No dimensions required. I'm doing it from scratch, so will be designing a template myself.