Came back here to say thanks fellas. Worked great, it's a whole new bike now! Had to loosen the front muffler to get the drill in line but took 5 minutes to so both. Keep up the good work!
Check out the length of the pipes, that's your first clue. There's also that and the fact that the circumfrence of the outlet on those stock sportster mufflers is much smaller than other Harley pipes. Get a decent tune and you still have enough back pressure. If anything it will breathe better with less heat in this scenario.
Not to mention that shotgun sound is one of the best Harley sounds I've heard off a stock set of mufflers. Want a similar sound for any other HD and you're looking at a few grand for some German made exhaust. Like a set of Penzl's for example.