Hanging a swing from I joist

[Jon Robinson]

I have a property that is built with I joist as the structural floors. There is a cathedral ceiling in the living room which sits off the kitchen and I want to hang a Jhula swing from the joist that span the section between the kitchen and living room. It is about a 20 foot section and there are already double I joist holding up this section, with the proper support all the way to the basement floor. My question is do you thing it is strong enough to carry an additional 300/400 lbs. also what would be the best fasteners to use for this type of joist? Thank you in advance.