I also think you're on the right track with a 7" cut. I installed the Black Heart crush delete section to our pipes and the instructs follow-
http://documents.holley.com/199r11143.pdf
I'm betting the Borla 60606 will bolt right up to my existing cuts and I also have a set of 2.75 sleeve clamps. A similar set of clamps was provided by Chevy (in a 2.5" size) on the 2010 V6 Gen5 Camaro. It provided alot of versatility (IOW- room to miss!). I think Borla's 2nd cat delete/X-pipe,part #60606 will bolt right up and leave me with a "Crush Delete" kit to sell on the owner's classified parts section.
Keep us posted on your progress- and remember to have fun!

You'll be doing away with the same crushed section right at the rear subframe, just beside the differential.