Hi, I have the Super Dragger on my R34 GTT. I have no issues with scraping and it sits up quite neatly under the bumper. From the side of the car you can just see the bottom part of the stainless steel muffler sitting under the bumper.
To install, it was quite easy, did it my self. It comes in two parts, first section is from the cat back, and is about 1.5 meters in length. It has a small silencer built in. The muffler section is about the same length and the two bolt together with 4 bolts and a gasket.
If you do go for the Super Dragger, be warned that the muffler is huge when sitting on your kitchen floor. I was amazed at the size of the thing. And in all fairness to HKS when its on the car its a really neat and small install.
The hardest thing with the install was getting the old exhaust off. Two bolts hold it to the cat and these usually have seen better days.
The sound from the exhaust has a bit of bass. not too much and this cools off when the exhaust warms up. From inside the car the exhaust is nice and quiet, and from outside gives a nice low sound.
If you stand beside the car and rev it, the engine is actually louder than exhaust.
Over all, its a very good purchase.
John