Obviously TT made changes over the years to their Dual Headlight Units.
Here's some additional TT Dual Headlight info from UKGSer, it's kind of dated, but simon thomas talks about warping parts of his TT dual unit by using higher wattage Halogens in his because his set up had plastic lenses, reflectors and other parts, whereas mine was made with metal and glass. He replaced the warped parts with Honda CBR CFR 400 parts w/ 100mm lenses.
Richie says "...word of warning though it ain't twin headlights its a single piece of glass moulded into two rounds with twin headlamps inside." That nothing like mine, definitely two separate headlights, which sounds more like Simon's.
You can read the posts here: http://www.ukgser.com/forums/showthread.php?t=44512