all of the lugs, the bottom bkt shell and the rear dropouts on your vitus are specifically suited for the given frame size.(ie- your rear dropout is specifically made for frames ranging from 58 to 60 cm in size)
on any lugged frame, each lug must correctly & accurately correspond to the required tubing angles, in this case the seatstay angle relative to the chainstay (ex- on a larger frame, the seatstays are set more vertically than on a smaller frameset) .
in order to obtain the best and most reliable join , pressed,bonded & swagged framesets like the vitus must be very tightly toleranced with little room for the fudging of join angles.
on lugged steel framesets using conventional brazing methods, the builder can do some minor adjustment when he mitres and/or files the lugs to fit the tubing (say +/- 1/2 degree or so on premium frames) and in the case of stamped & welded lugs, even bend them slightly to fit. even so ,most high quality(ie-non mass production) frames will require a number of different lugs,btm bkt's and or dropouts of varying join angles in order to complete a full size run of any given model.