I have chatted with a few people on here who have stated that cutting the muffler out and welding in a 3inch in and 2.5 inch out to the stock pipiing works fine.
I am doing the same route as well.
I have no doubt that welding this way will work, you will just fill the gaps with weld. I used clamps for future removal if necessary. I am only saying that the factory muffler for dual exhaust on a 2010 is 3" in and 2.25" dual out and that the tail pipes are 2.25". Also, unless you are welding in a 26" muffler to replace the stock one, you will need an extension pipe.