You need to peel back the rubber hood and the bolt is located on the outside of the STI near where it says DuraAce. It's a 4mm allen key I think. Might be a 5mm though. Can't remember off hand but it's one of the two. Someone to confirm?
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
The clamp bolts for all of the STI shifters I've worked on are located under the rubber hood on the outside face of the body. Look for a groove that disappears under the rubber. Follow it and there is a bolt that takes a 5 mm hex wrench. Stick the hex wrench in there and loosen the bolt and they come right off.