To answer your question, I think the handling is off. That is, I think that the stiffer rear creates a little more sway in front. Additionally, I think that the stiffer rear slightly changes the weight distribution of the car, so that a bit more weight is on the front, making it ride a bit lower - compressing the springs a bit more than it should and fomenting a touch of toe-out.
Further, I'm wondering if when you put in HD's, you need a stiffer spring to go with it. That is, in the rear, where I have th HD's, I have stock springs. The harder and stiffer rebound of the HD's might be a bit much.
What do you think?