Are the 4" risers straight or pullback ? i'm guessing straight.
The difference should be fairly small, maybe 1-2".
Dont forget, a lot depends on how you have the bars adjusted in the riser clamps.

 

Maybe you can sit on bike, and grab a measuring tape, and put your arms / hands up to approx the height you want. You might need someone to hold tape.

Because of the rake, the higher you go, the more pullback you will have if you keep the bars following the line angle of the forks.

You'll only pick up the angle of the rake with straight risers. Just hold a straight stick in line with the forks and you'll see how much it comes back. Wide glide style front ends come back further than touring models.. I suppose you'll want the 4" risers you sold me back now.. LOL...