I just bought an Interstate ICM, Interstate carb springs and a 4 Degree trigger wheel. Hope to get it all installed this weekend. As I understand it, it's best to use no more than a 4 degree trigger wheel if you're also going to use the Interstate ICM, as the ICM gives you 2 Degrees.
The I/S icm does not give an additional 2 degrees. the curves are the same. the I/S icm just has a steeper advance ramp to 3k rpm, than the std icm. the base idle advance of 3.5 degrees is the same for all bikes. Goldwing GL1500s have a base idle advance of 0 degrees and why/where the 6 degree TW came about and worked so well, plus it has more total advance and uses a vacuum advance system, all for maximum MPG.
factorypro.com recommends no more than a 4 TW for valkyries.
see curves
http://timskelton.com/valkyrie/tech/trigger_wheel_plus_dyna3000.htm