Well it seems there were more than a few shadows in the shed last night because in the clear light of day I have to report that they are in fact straight veins, which means they're uni-directional.
Go to the back of the line Sambo.
Thanks for the replies lads.
Craig - I have a question for you on the R32/R33 rear ends. Geof Hemphill seems to recall your brother John 'refurbishing' all the bushes/rubbers/boots on the GTR rear end after heavy track use. Do know much about what was involved? Mine's in decent condition but I'm thinking of taking preventative measures.