thing is that flattys are higher as standard anyway, so to go down 50 would probably be the equivalent of a 40mm drop on a vt.
there is a thread somewhere will try dig it out for you mate.
http://www.saxperience.com/forum/sho...d.php?t=141903
found it, doesnt have any flatty's on there though, but it will give you a better idea i guess..