- Reduce the weight in the handlebar bag.
Absolutely. You have a 5 pound pendulum mounted high and on the steering mechanism. Make it a LOT lighter.
As Ronk says, you've got some big chainrings. a smaller granny can help; I've heard of people going to 26 and (sometimes) 24 rings...
If your crank has a separate 74 mm bolt circle for the granny a 24 or 26T chainring is a great help. I've done it on numerous bikes and it works well.
Misinformation too about STI and sprocket size. It's the dérailleur which limits the cassette range - use a long cage dérailleur and you're set.
More misinformation here. The derailleur does limit the maximum cog size but the cage length has nothing to do with it. A long cage road derailleur won't accept a larger cog than it's short cage counterpart, it will only wrap up more chain and allow a larger total tooth count.