Sean D. Tucker 's Challenger is a highly modified Pitts. You can check out www.poweraerobatics.com for some pictures. The only company that I know of that has kitted this airplane is exclusiv-modelbau a German company..I believe they have a link at desert aircraft..
Sean Tucker is IMHO the absolute best aerobatic pilot...he doesnt' explore the limits..he busts right through them.
-Anton