3x decent (old DA or campy Rec-C) stainless cable clips and route along top tube, cable outer ON TOP of top tube, as those clamp things will rip a hole in your nut sack if you turn them upside down. And just be mega finicky about cable housing length & curves, you can make it look good, but it takes trial & error & swearing in the shed.
OR
saw a picture of a rear brake caliper located on the chain stay bridge (in porn between all the bitching), with some finesse that could be made to look tidy & inconspicuous.
I'm thinking either....
3x decent (old DA or campy Rec-C) stainless cable clips and route along top tube, cable outer ON TOP of top tube, as those clamp things will rip a hole in your nut sack if you turn them upside down. And just be mega finicky about cable housing length & curves, you can make it look good, but it takes trial & error & swearing in the shed.
OR
saw a picture of a rear brake caliper located on the chain stay bridge (in porn between all the bitching), with some finesse that could be made to look tidy & inconspicuous.