My Bianchi came with open brazed-on cable guides under the BB, and my 1980 Peugeot came with a slick (so to speak) teflon under-the-BB cable guide. I do use a piece of old school Campagnolo stainless steel housing under the BB of Capo #1, to adapt it for use with a newer front derailleur which lacks a cable housing stop. None of these systems has ever given me any problems whatsoever.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069