Major? No, but it may undo some of the handling change you're trying to achieve. Adding 3cm to the fork will raise the front end of your bike by that amount. That will make the head angle shallower and lengthen the trail somewhat. It may not be anything significant (I'm not going to plot the difference) , but it's something to consider.

It will also raise the handlebars by about 2cm vs. the seat (as you raise the front end, the seat also goes up with respect to the ground (but not the pedals), so you might factor that into your choice of stem angle.