Found a better picture of it on Wouter's site--check out rigging photos of the Taipan 4.9 boom toward the bottom of this web page:



http://www.geocities.com/f16hpclass/ahpc_taipan_49_how_to_rig.html



Seems like your could copy this system on any round boom. (Can't tell you how well it works, though. Heck, my boat doesn't even have a boom...)