How do I prevent STI shifter cables from blocking access to my Randoneering Bag or Handlebar bag?
The best solution is probably to move to either a different shifter setup like newer shimano 105/ultegra or SRAM (with cable routing under the handlebars) or to a barend setup like most randos employ. I know this isn't your preferred solution, but it's probably the easiest and most effective. If you mess with the routing/length on your shift cables, you're going to start experiencing shift slipping and improper shifting.