Since i havent made a ton of fruit beers i cant say for certain, but i have done a massive, repeat massive, amount of research and putting the fruit in the secondary is the way i keep coming up with. That AND adding extract. I ask pro brewers as well and they secondary or bright tank something or other but certainly after fermentation. The problem is if you add it in the boil its not bad, just different. Same with primary.
The problem is putting fruit in with the whole yeast cake will lead to diminished flavor and scents from the yeast refermenting. I have all kinds of plans but havent gotten to it yet. Juice in the secondary seems a good idea. Also freezing the fruit to break open cells. That and adding some extract would create a very fruity beer. The raspberry blueberry beer i made was in boil i think and it came out good. Problem is fruit can be expensive to. I like juice idea.