Any reason you don't just go for the commonly available rack and side rail fitting kit?
Yeah I could easily do that. Not that fitting panniers bigger (Givi TRK33s anyone?) than Givi's specified E21s has ever overstressed anyones Givi side rail fittings (obviously Givi simply cover themselves with their stated E21 pannier weight limit for the PL349 side rails).
According to Givi the Wingrack together with its FZS600 fitting kit weighs a massive 7.5Kg (don't know the figure for the Thou) so it lends itself better to an 02-05 Thou than to the 600. But it does turn the 600 into a load lugger instead of the fun bike that it is.
But sure - around 7.5Kg of racking even on the Thou is a lot of weight at the far back of the bike to be carrying every time the bikes ridden.
Yup, looks like the PL349 side rails are the way to go on this Joe