I have a Dr. D full system on my 09 now. After riding my friends 09 with FMF mega system I like his better with less hit down low and more on top. My question is will a 4.1 slip-on or any other slip-on system fit the Dr. D header ? I have put an 06 muffler on it and it seems to bolt up and seal ok (haven't rode it at the track yet ) I would like to keep the rad.lowering kit if possible. I heard the factory forward header works but can't confirm it. I only ride mx. thanks in advance.