Paul, thanks for posting the link to Dharma trading. That is exactly where I bought my silk back in July 2010. I've just checked and I had 9 yards of 36"wide 5 momme shipped to the UK for $24-85 back then. great value!
I've since used it to cover three 60" plus span models, two 42" to 48" models and two 36" span models. That's a load of covering for the money and I've still got quite a bit left on the roll.
Michael, you won't be disappointed if you use it on the Harrier. I covered my GWS P-51 after having flown it in bare foam for a few years. I took the opportunity to upgrade the motor and the airframe is really far more resilient with the silk in place. It doesn't add a great deal of weight either and it makes adding a colour scheme so easy.