Just to be clear that bolts on the underside of the BB, making the gear cables run underneth the bike?
Yes
I've seen frames with the braze-on you describe for both front and rear mechs (attached to the top of the BB shell). Why is there no braze on for a front mech (is it a very old frame?)
Yes
I've seen frames with the braze-on you describe for both front and rear mechs (attached to the top of the BB shell). Why is there no braze on for a front mech (is it a very old frame?)
Would this work?
http://www.bikepedlar.co.uk/acatalog/Front_Mechs.html