It's low, all the Manns seem to be. The swingarm is much more complicated and I think longer, the bike is long. It's better handling than even my KLX, it's just very intuitive and surefooted. I couldn't really imagine anything handling better, but I'm not much of a rider. The rear shocks are bit soft though. The mark 4 was made between 81 and 2, less than 20. One other surfaced on ebay about 18 months ago, but the frame has been altered. I recognized it due the swingarm
All the Manns are non metric on the bolts.
http://www.lt-racing.com/html/dms_tt500_yamaha.html is pretty much the only source of info and it hasn't been updated for a while. Dick Mann told me mine is a mark 4 but the website states only 3 marks were made. I think there were over a 100 of the mark 1s
Mann had tanks made from mark 2 onwards but the tanks change slightly with each mark. They are really rare, Mudmantra in northern California has a mark 2 with tank and is a moderator on
http://odinxt500.freeforums.org/technical-section-t553.html, on that site hardly anyone apart from Mud rides offroad