Hmmm. Sue, I tried it on 6mm needles, but thought it was too open for the look I wanted. At 5.5mm, the unblocked scarf width already measures 12", unstretched. (I wanted to end up with about 13-14 inches width, blocked, and about 50"-55" long.) It seems to stretch more widthwise than lengthwise (would that it were the other way around!). I ended up at Loop today in Islington (I'll have to go to I Knit sometime else, what a shame! ), and the very nice lady there said she thought it looked like my tension is "fairly loose." Is that why I have more stretch widthwise than lengthwise?
I'm worried about making the length I want, at this point -- though I'm having a difficult time gauging how much yardage I have left on this skein of mohair laceweight, it's so light I can't eyeball it correctly. I have two skeins, so hopefully that'll be enough, do you think?
Off subject, I have to say I'm really enjoying this adventure of learning to knit, but it might beggar me! Today at Loop I went ahead and bought a pair of rosewood needles from Lantern Moon and a set of circular needles from addi, plus a Lexie Barnes case to put needles in. They're having sales on their mohair/silk/nylon yarns (3 quid!), so I may very well visit and buy again later to fuel my mohair addiction...although they had some really lovely Australian merino yarns on sale as well, and even though my tension isn't quite good enough to set needle on such beautiful stuff (which is why I'm not buying the really nice mohair yet), it was veeeery tempting to get it at 50% off!
Thank goodness I'm on the road and have to keep my wardrobe at the minimum, or I'd have spent hundreds on yarn and needles!