When the 900 fireblade came out in the UK it had a 16" front wheel and the first mod that everyone did was to change to a 17", better stability and not as twitchy also a much better selection of rubber. Willie is right about rear ride heights but it is only a very small amount and you may not even notice a change in the handling best bet is change it and give her a try if I remember correctly it is dual shock with no remote resevoir on the rear so shorter shocks shouldnt be too expensive.
Cheers OZ