Coach to Rome

A friend is thinking of taking  the early morning (6am RomaLinee coach from Cupramarittima to Rome) on 7th August. Has anyone any experience as to how well it sticks to the timetable of arriving in Rome at 9.15? He has to get to Fiumicino for 11.15. Any advice is much appreciated.

Very limited experience of any bus to Rome, once in fact and it was spot on time. However it is the main holiday period and being over cautious on such things, I would be personally happier with an extra hour. Perhaps the hour if not needed for travel will allow a leisurely breakfast and read of the paper