I just ckecked: the Z4.5/400S is 30 Gramms heavier and 3 Centimeters shorter, so about same same
Hmm,
300PF with FTC II : 971g (weighed without collar as that is optional), length ca 18 cm with FTC II adapter.
Roland's list:
400/4.5 S weight 1245/1160 (last number without tripod foot?) length 234.5 mm
That is some heavy 30 grams, and long 3 cms

So at best 400/4.5 S ca. 200 gram heavier and 5.5 cm longer - it compares closer to the 500PF without FTC adapter.