I have one on my 87 SunSport. It's absolutely amazing and worth every penny. The tubing is the same size as your exhaust, they are made to spec for your boat. Mine measures 20.5" below the swim platform to the tip of the exhaust below water. 12" below the current exhaust outlets.
Closeup during installation:
http://photos.wakeboarder.com/data/3...90425_0554.JPG
http://photos.wakeboarder.com/data/3...90425_0537.JPG
http://photos.wakeboarder.com/data/3...cture_0031.jpg