One word of warning.

When I set up the OCR for Ventoux I had a short reach Tiagra Derailleur fitted and 52/42/28 as the rings. Set up the chain for correct length for 52/30 and that was fine. But when I tried to get 28/30 I had a Rattly noise. It was the derailleur cog hitting the 30t ring. No problem-I had a 26 I could fit on the crank and I could go 11/28. Did that and I still had the same problem. Had to run 28/28 and it ran very close to touching again. used that so watch out for the derailler touching the cassette if you are running a short reach derailleur.

That gearing got me up the hill but at one point I did want just one more gear.