Deuce risers are 5.5", not 4". (and do require rerouting of throttle cables)
A four inch riser should work with no alterations on any valkyrie..... and the throttle cables on the interstate exit the handlebar control housing higher (with a tad longer reach) than on the std/tourer models (which exit at the bottom).
Sorry, I don't have my bike handy and assumed Deuces were 4 inches. I apologize if I misled you.