This particular muffler guy said he would install double walled pipe IE. 4" outside diameter and inside 3" diameter. I do like the idea of extending it an inch past the stock.Since you're considering the whole she-bang, consider installing the tips further out than the stock locations. On some cars this appears to influence the amount of drone inside a car, but it's not clear if it's a matter of where the outlets dump with respect to the bumper edge or if it's simply a matter of ending up with a *slightly* longer exhaust path that is enough to change the resonant frequency of the exhaust tubing.
One car in particular had long tubes that were "filled in" at least 2/3 of the way to cut down in interior noise (otherwise the "flaring" of the tubes with respect to the exhaust piping would create a "booming" which in stock locations would resonate too much inside the cabin). A popular mod was to install pre-production style hollow tubes (ie. outside and inside diameter being equal the whole length of the tube) and installing them an inch beyond the stock location.
So I'm wondering if the "tuna boat" syndrome on our cars would be addressed by simply extending the tips an inch or two past the bumpers, allowing the removal of the resonators without fear of setting up that standing wave inside the car that seems to be the nature of the dreaded "drone".