Its not a bad area not so much the national park but the area west of theres an old Ghost town Addamsfield used to be a mining town, you need 4x4 to get to it.
Also the logging roads and following the power lines around that way there are some good tracks.
try this link this book would be the best track book on tassie it does miss some but on the whole pretty good
http://www.roving.com.au/body_index.html