Swing-arm centre sheeting

Not quite - I think if you search for images of the 'Elementarry' proa designed by Rob Denney you will get the idea. I think he used box section carbon booms bonded directly to the masts. Significant reduction in hardware too.

I would post a picture myself but I am on my poxy iPad and can't figure out how to make it 'just work'.

It is true that the Laser mast and boom rotate together but the end of the boon can still flap up and down - that movement is still controlled with the kicking strap and sheet. I am suggesting fixing the boom absolutely rigidly to the mast and it having a deep enough section to act as an effective cantilever.