What happens when I share duplicate perks?

In the new fallout 76 game its possible to share perks with your teammates. As taken from an interview with developers:

Sharing perks

Once you put at least three points in Charisma, you’ll have the
opportunity to share active perks with the rest of your team. As long
as your Charisma is three times the point cost of a perk card (for
example, Rank 1 of Green Thumb costs 1 point, so you could share it
with 3 Charisma. Rank 2 costs 2 points, so you would need 6 Charisma,
and so on) you’ll be able to let your team reap the benefits of your
card, and use it to plan effective strategies to synergize available
perks.

What would happen when I, for example, take a perk like “Shotgunner“. Which at level 3 adds 20% to my damage done with shotguns. Let’s suppose I’m playing in a 4 man squad, I convince everybody to get level 3 shotgunner and to share that perk with the team. Would those effects stack? Would the entire party now deal + 80% damage with shotguns? If this stacking of perk cards is allowed how would that be calculated?

Let’s say I have a shotgun that has a base damage (without perk card) of 100. I slap on my own perk card that increases its damage from 100 to 120. If my teammates share their own perk card would that stack on to the base damage of my shotgun? So + 4*20%? The way I see it (all assuming the cards stack) are as follows:

100 Base damage + 80% of all perk cards -> 180 damage

100 Base damage + 20% for my perk card -> 120 damage + 60% for shared perk cards -> 192 damage

100 Base damage + 20% for my perk card -> 120 damage + 20% -> 144 damage + 20% -> 172.8 damage + 20% -> 207.36 damage

Tldr: Is it possible to stack multiple perk cards when shared with your team and if so how does the calculation of the stacked bonuses work?