Anybody built or installed a underbody rear air diffusor on their HHR? Most of the "universal" or those used on similar sized cars that could be modified to fit are $300 to $750. Typically $500 for decent quality. Seems like a clever fabricator could yield a decent looking unit. The stock rear plastic cover looks like all it does is catch air and "flutter" at high speeds.

 

I'm looking into this as I want to install dual exhaust which will necessitate a modification and possibly a weaker right bracket that helps hold the rear cover. Standing still it has no purpose but at speeds I suspect it keeps the cover from flying loose. If my fabrication weakens it, I'll want to reduce the parachute action and flutter that takes place here.

If anyone has been here before or has ideas, post up.

 

A guy on another forum did the split exhaust and had cut the sides to do what you're thinking I believe. Pm me.