Has anyone used these and what do you think of them?

I have thought about using them, but the idea is too scary . It seems to me that if you are removing a degree of the springs' effectiveness, the whole system will be upset. Factory spring rates are set by the factory after lots of experimentation, and, admittedly are a compromise.

IMHO it would be much safer/effective to use correct, i.e. lowered, springs, as the rates for them are also worked out.

what he said i would only uses them for a static display at a car show! to dump the car in the weeds!

or... for a short time to increase the height if i had to go over the pits hehhehe

Looks like it's up to me to give it a try and let you know how they go.