No, certainly not 4".  That will put essentially no weight on the front axle.  I don't think I've ever seen a tractor which had 12k on the steer with no trailer hooked up.

The numbers I used were just made up, but they are pretty reasonable, and 24" ahead of the center of the tandems would be approximately over the front driver, which is consistant with all the trucks I've ever been around which were set up right.