page 3: z=0.24671 ref Carilli et al 1992 (not Darling 2004) 1 mas = 3.87pc (not 4.8pc) (added a reference to the web-based cosmology calculator) page 3: footnote removed; this info is in Table 2. page 9-10, section 7: expanding the discussion of the fitting of helical jets. Added Figures 8 and 9, and Table 6. page 5, added description of components; insert Figure 2