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Thank you @nelzie! I never have run the CCC race, just the TMB three times.
The most difficult parts in my opinion are the Col De Voza, it is a really difficult start to the trail, then the from Notredame De La Gorge to the Croix Du Bonhomme and then the Col De Balme in Switzerland. I hope to post the next section by the weekend, sorry for the delay. I have been working daily on an art piece and then training late evenings to night. Have left me too tired for any kind of social media activity. But the next section is nearly finished, I am happy to say. Thanks for your comment and support.

Thanks for your answer. Whenever you answer, it is appreciated :) UTMB route is CCC+TDS with slight changes. My husband had TDS and OCC (OCC is half of CCC), so half of CCC would be half "been there, done that" he hopes :)
The first places that you mentioned near Les Houches he had during TDS but opposite direction :) The race began in Cormayer in Italy and finished via Les Houches in Chaminix. During TDS he had difficulties somewhere around Col de la Plate (Italian French border I think) and after, and most difficult was Le Contamines (near Notredame de la Gorge that you are mentioning, but we see that UTMB and TDS are not completely the same routes in that area).
Anyway, the Col de Balme ( actually area near Trient and Les Flegeres) I think that he had during OCC. OCC start was in Orsieres, in Switzerland. He agrees Trient area was difficult.

CCC begins in Courmayer in Italy, and goes via Switzerland, to Chamonix.

Hi Nelzie thanks for all the information on the various races, much appreciated!
So with the various races your husband has done, he has experienced most of the UTMB anyway. So with hard training he has a very good chance of completing it as the big race itself will not be as daunting to him as it would to someone who has never been there before. So he should go for it!