The Cusco hangers were a bit of a pain to install. I just used some WD-40, sprayed the mount and the inside of the hanger and they went on pretty easily after that.
I have all four on my car. I would definately recomend them to anyone with the HKS Car/Ti. I know with mine, the exhaust hung a bit low and would "wobble" around with the factory hangers.
Once replaced the exhaust sits a little bit higher (looks better IMHO) and is very stable.
I checked to see if the exhaust was hitting anything, but it still clears with ease. Also with the HKS there were no modifications necesary to use the Cusco hangers.