Chris
I am going to be very cheeky and say that you need Sandra Niessen's amazing book Legacy in cloth: Batak textiles of Indonesia - the result of 30 years of field work and research in 568 pages!
http://www.bataktextiles.com/projects/Legacy.html Sandra covers technique in some considerable depth; in particular see 'Part IV Technique' in 'Technique 7 Decorative Weft' p499. However, patterning comes up all the way through. In the Catalogue section there is Catalogue 7 'Weft Patterning' p366.
Sorry, I am a terrible cheer leader for Legacy - but unashamedly so!
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Pamela
http://www.tribaltextiles.infoon-line tribal textiles resource