No I would not say to build the whoopie onto the hammock, as then should you want to wash your hammock you also have your whoopies tossed in the laundry and that can tangle them at very least. Your whoopie should have a fixed loop at one end. Take that loop though the channel and then pass the end of the sling through the fixed loop as it exits the far side of the channel and tighten it all down. This is a girth hitch and the simplest way of attaching whoopies to a channel end style hammock.
No need for an extra loop and carabiner as they are only extra stuff that is not needed.