Just checked out the yarn over at jimmybean and that gauge (HUGE!) doesn't allow for lots of options. Wondering if you unplied the ends to be joined and then did a sort of felted plying of opposing ends. Make sense? Seems the key is to get diff strands going in diff directions so the join can't pull apart. Try a test on scrap piece...unply and see if you can retwist them (using moisture on the ends might help them 'felt').
Just an idea.
Keeping to the knitting basics