I abandoned the idea of knitting a tunnel, instead i crocheted a ribbon of slipstitches with holes, to pull the cord through. I tried to crochet an icord, but wasn't satified with the results. So i made a chain of 75 cm. with one round of slipstitches. That made an easy and nice cord. At the end i crocheted corkscrews. Took me some frogs, but the curliest result was 4 crochet in 1 chain.