I would try to find a better strut for any kind of lowering.
is my review of dropping them with stiffer springs.
There isn't much bounciness around town but at speeds there is and it can get annoying.
Also, when lowering your car, you should shorten your front endlinks. Lowering pushes the sway bar ends up past where it was designed to be effective. This could weaken the sway and/or add to your spring rate.
This would entail:
1. Measuring from the ground to the bottom or top of the endlink on stock suspension
2. Installing the lowering springs
3. Taking the same measurement
4. Shortening the endlink by that amount
You should/could do something with the rear but it'* not as straight forward.