As I have already mentioned to Simon, I believe that his Jibboom pivot attatchment point is incorrect.
We noticed when rigging that he had two loops on his jibboom for attaching the pivot to.
I am now convinced that it was fixed to the aft of the two - this would increase substantially the leverage and hence tension down the jib leech.
Having spent some time investigating this as well as discussing it with Matt, it is clear that the jib leech tension is dependant on two things i) Jibboom pivot point(leverage) ii) Rig tension.
I have seen photos of BR sailing in moderate breezes and the jib shape sets perfectly.
Therefore adjustment of pivot point &/or rig tension should alow correct setting(in moderate breezes).
In light winds a different set of perameters come into effect, such as the weight of the jibboom. In these conditions I will be setting the jib conventionally and resting the boom on the deck.
Hope this helps.