250 ccm is enought for begining stunt.... look on youtube what reza ss from asia do with ninja....with different gear ratio-different sprockets on our ninja we get pretty exciting motor....I would use cage for racetrack,parking lot practice-gymkhana
and some basic stunt....I don't want spend lot of money on frame sliders which,in some cases,can cause more damage than be usefull and for little more money I can get a cage which offers much more protection...also,I ride ninja all the year,that includes winter-rain and wind and roads in my town are slippery even in summer so I think I'm gonna fall from ninja few more times....