Can't speak on raspberry, but the peach ale I did a while back had 5lbs. of fresh peaches in secondary. It would have been less after skins and pits were removed, but this "subtle" fruit was overpowering, IMO. No one that tried it thought it was too much, and they couldn't get enough of it. I've never used extract, and don't plan to. I don't think that you can over or under do it with fruit for the masses, and that is what I make a fruit beer for as I could take them or leave them. But, it keeps SWMBO happy.
Looking forward to brewing some beer