If the guy you're having do the install knows "anything" about mufflers...he should have no difficulty making the exhaust modifications you want. All it usually takes is "time" and "money". A friend of mine installed a "magnaflo" system on his sierra a few years ago...and although it looked great with his "own modifications"...the first time he went off-road, he modified it a little more by ripping about 50% of it off the truck. Of course, you could always return the Roush system and purchase a different muffler which "does" exit the side (the borla system works, and they are a pretty good product). I think Roush gets a lot of push for our Raptor upgrades because they are recognized by Ford as an "accepted vendor"...one which Ford has personal experience with (I suppose that means they are "sanctioned" in some way...if that is the correct reference...). In any event, good luck with the mod and let us know what happens.