There is quite a bit of info on the Balearic slings if you look back through the archived posts (set the search to 999 days). We've had intermittent contact with a few members of the modern day slinging association on the islands.
The Federacio Balear de Tir de Fona has a nice website up at:
http://www.tirdefona.comQuite a few of the english pages are incomplete, so it helps if you can read or at least decipher Catalan. A good tutorial on traditional sling construction is at:
http://www.tirdefona.com/Ingles/marcoing.htmSuitable substitutes for "pita" would be sisal/hemp/jute cord. These slings are built solidly enough that they don't require unreasonable strength in your materials. The design is of course adaptable to synthetics as well, and is essentially the same as many of the methods posted here in the articles section of the site.
I like the leather binding on the pocket and retention loop. Functional and makes for a nice looking sling. These _look_ like a design that has been refined over centuries of use! More pictures at:
http://www.tirdefona.com/Ingles/marcoing.htmMatthias