OK, now before i start with this, i know all bikes, even of the same year, make and model are different, so no aspurtions cast here.
I originally sold my Fazer to a mate because i wanted a nicer example, i found one which has been Ivanised by Ivan himself. Unfortunately on bottom end, and 6K rpm roll on tests with my original bike, the new one was found wanting (so i sold it and bought my old one back). So i would say that my bike has a good bottom end as is. I'm a little suspicious that it may already have an advancer fitted, or maybe its just a "good" one. Either way, i think i'll let sleeping dogs lie and not bother fitting one.
Until i can meet up with someone who has one fitted and try a few roll on tests as a comparison.