You'll have to either pick up something that's a uniform 28ga wire to get it under the inner diameter of the paracord or be ok with cutting the plastic sleeving off the wire before sleeving with paracord. 550 is the biggest diameter paracord you can get. That being said, there's nothing wrong with trying to find some other mono or multi filament nylon sleeving to use that would look similar, too. Also, as mentioned, mdpc (when he's back), techflex, carbon fiber, kevlar and a bunch of others will expand bigger for you to use what you currently have.