I never heard where the Jefferies tube was supposed to be running until Franz Joseph made them climb up to the nacelles. I think I read somewhere that Jefferies had "intended" it to run up the spine of the connecting dorsal. I don't remember where I saw that or if I'm even remembering it correctly.
Andy Probert intended the D's Jefferies tubes to go up the center spine of the dorsal. I never heard any suggestion like that previous to that.