two options come to mind.
1. Use the mango rind instead of the mango fruit itself.
2. Use mango juice in secondary.
if you don't want mango to take over your beer, you're going to have to avoid using a lot of mango juice. that's why i think the mango rind may add the essence of mango without making your beer a mango beer. but, with all those fermentables in the sweetness of the mango itself, it wouldn't be a bad idea to add a tiny bit of juice instead of sugar at bottling/kegging for another mango dynamic.