you got it with the bar lenght would be better using the bigger bar though the small bar on the 11 will be a bit hard as you wont get the bigger trow to turn kite quickly other than that the big bar on the 9 well you wont have to move the bar far as it will turn so quick . as long as they are the same year or close too some have a different safty ie front line flaging make sure the flaging line is long enough for the 11 meter to depower .so yes i would use the big bar for the 11 on the 9 but not the other way .hope this make sense .