Well I have a custom and I don't know if they are exactly the same as the classics, but there is no way my 35" drag bars would work on my custom without my riser extensions. Without the extensions my controls would hit the tank big time.
My risers have a total of 5 1/2 inches of rise to them (factory risers + riser extensions). Which is just about perfect, the controls come about an inch away from the tank. (with the handlebars turned all the way the hand controls are actually above the tank.)
The riser extensions bring the bars & controls up over my tank so they don't hit when turning. My drag bars have 5" of pullback.
I can grab some pics of my setup if ya want...
Like I said, if yours is similar to mine I don't think it will work, unless you put on new risers too.