Nah it doesnt sound any different. There was a guy's webpage I seen one time. He had a 99 Trans Am i believe (LS1 TA) with 2.5in true duals traveling side by side in the stock catback posistion and then over the axle and out the way your talkin.

 

Hey, I am the guy with the pipes under the axle. LTs with H-pipe bullets and then run under the axle and out the rear. Clearance is a non issue. I always jack up the side of my car on the SFCs and they way the exhuast was put it the axle does lay on the pipeing but there is no ill effect. I had them weld a hanger on the piping at the rear seats and then bolted that thru the car. I can not move it no matter what kind of force I use. and then used the stock hangers in the rear for the support after the axle.
There is no fear of going over a bump and it scrubbing or hanging up. The relation to the axle never changes. I guess in a VERY HARD stop it might contact the axle but if you have to apply the brakes that hard I doubt you will car the exhaust is hitting the axle.
Please post more questions about my set up if you have any. I do not have any pics. but it looks very cool from the rear, it Vs out from the rear end, the pipes are near the V of the sway bar and I had him tuck them up so they are not seen, painting them black masked them really well.
There are several cars running this way...

 

Mike,
Contact SpeedInc. They have a shop car that has true duals on it. They also have some really nice stainless mufflers on it too.

 

I too have had no issue's with ground clearance except for the one bend for the trans support. I'm very happy with the work the guy did. I really want to post pics, i'll try to arrange it soon. thanks Tony