I would say the RdC Is a hard sportive, the cobbled climbs give it a distinct flavour and make it tough on the bike/trike. Having said that it is still only 75 miles and it all depends on your recovery rate after the climbs. I found that (I didn't complete it remember) the cobbles make the climbing harder but they don't go on for ever and on some of the gradients really add an edge. I did ride 75 miles that day and when I had got back to the campsite felt I could have still gone out and had a good ride, I took the dogs for a walk on the moors instead. I haven't ridden many sportives but find that any ride is as hard as you want to make it, that's why I took the trike. It's a good challenge and I will be back to give it a real go with slightly down-gunned gearing and up-gunned brakes. Hardest? I haven't done them all and we all have different abilities and ideas on what makes a ride hard, also it sounds like (on the other forum) some have to defend their last effort by dismissing other rides as easier. I do recommend it to anyone who likes to sweat and has a strong bike, spectacular views and a sense of achievement no matter what.
, I suffered this year then suffered a bit more, Dodlee I think