Comments on Beretta 390 Slug barrel??

I just picked up a really nice Beretta 390. I have located a pretty good deal on a factory cantilver slug barrel but dont know how well they shoot. Does anyone use one of these?? I have heard that you need to use a 50mm bell scope due to how high the cantilever puts the scope>> I've always been a Remington guy but I like the feel of this gun..