i would use mangos in a secondary fermentation. adding mangos in the boil can cause a pectic haze. if you use to much it can cause the beer to be tart. ive found that fermenting with mangos will also decrease the bitterness a bit so adjust for that. in my mango habanero ipa i use 3lbs of frozen (trader joes) mangos per 5.5 gal in secondary..thaw, sanitize bag/scissors, add to secondary, and rack beer onto them. you will loose a good amount of beer to the fruit mush. i suggest using citra late in the boil and dry hopping to help up the mango intensity.