This was a case of non-intervention on my part. By the time I showed up, everyone working on the movie had adopted pronunciation of various names and terms based on Present-Day English habits. I put my foot down over the pronunciation of Hrothgar as /roθgar/, but I decided to say nothing about /skop/ because there is a good chance that it's a more accurate pronunciation than /∫op/.
Yes, I'm fully aware that Anglo-Saxonists are taught to pronounce most instances of sc as sh, especially in word-initial position. But first, this shift almost certainly hadn't occurred in the early 6th century. And even using later Old English as our standard, if Donka Minkova is right, [∫] may be wrong, or at least innovative, even in late Old English. See Alliteration and Sound Change In Early English pp 130-3 for her arguments that [∫] lacks phonemic status as late as the mid 11th century, although it certainly would have enjoyed allophonic status somewhat earlier. Note particularly her assertion "the cluster /sk/ remained bisegmental in all environments in Old English." (pp. 132-3).
<sc> certainly does assibilate eventually, but if we can't be certain that it changes until the 11th century, I felt perfectly justified in postulating that it was still /sk/ in the sixth.