According to the Honda owner's manual, the gap should be 0.60 - 0.70mm (0.024 - 0.028 in).
Under the right side (as you sit on the bike) side cover.
You can, but it will require cutting and adding framing on the front and lower part of the engine cradle. It's really not worth the trouble unless you have lots of frame and design experience. Sorry.
Stock 2009 CMX250 Max speed is labeled at 86 MPH.