I used 6.5# of strawberries in my saision (see recipe database).
Chicks salivated over it, and I am consistently asked to brew it again.
I used 5# of 'mixed berries' which was raspberry, blackberry, and marionberry (joke's been over done already). Sadly, they could not overwhelm the hops and it was decent, but not good enough. I would either 1) cut back on the hops, or 2) pump up the fruit.
Mind you both those fruit additions were being added to a 40 IBU beer. It all depends on strength of the fruit, and how many IBU you have to overpower.