Believe it or not a got an award at a vjmc meeting for the 250 and they announced it as an 1100.

I have done a track day at oulton park on the 400 and I over heard somebody saying they beat that 1100 kat

on his 600 Honda.
I was thinking of a bit more detail to the differences, I have heard people asking what will swap,and there is not a lot. Of the top of my head I know the fairing, screen, indicators, tank, seat, rear mudguard will swap,the 400 side panels will fit the 250 but the 250 panels will have to be modified to fit the 400.The fairing bracket is different as to is the headlamp.
Even the batteries are different.