Ended up fitting it to my HPL boom instead of the Fiberspar. Will be used for 9.5m & 11m Formula. The Fiberspar has a buyer lined up and will be replaced by a 2011 NP x9 225-275, got offered a deal I couldn't say no too:
Pulleys fitted and waiting for some light winds. Looks better in the flesh and feels very solid. Hopefully this might help any body else thinking of trying this:)