My bike has 9 spd tiagra sti's on it and I only got around to doing it a few years ago when I did a big overhaul of the whole bike, including new housings. Took some photos before to recall the general housing layout, and don't recall any real head scratching to get it set up right. I can ride the bike no hands for ages so the housing and headset overhaul must have been good.
still have one bike to switch but it was overhauled with the original idea to go to someone else so left it as is.
I would only recommend doing this if you have the strong instinct of front brake = right hand