I don't know about "sites" but a search through the various HT threads for each year should provide most of the info.
Difficult bits: I presume you mean likely to be unrideable either in part or as a whole section
Ben Alder Singletrack, mostly rideable, just watch out for the water bars!
Corrieyairack Pass, the last zig-zags will be a push for most
Loch ma Stack, maybe 1km along the loch side boulders
Bealach Horn Loop, Gobernuisgach Lodge to the split boulder at Lone
Ledmore traverse from Suileag bothy to the road at Ledmore junction
Not sure about the new bit after Ullapool to the Dundonnell Road
Phil should know about the Loch a Bhraoin - Loch an Nid track, I've not done it.
Strath na Sealga - frustrating due to lots of burn and drainage crossings. The river crossing is OK so long as it's not in flood and/or there isn't a strong upstream wind blowing.
The climb over to Carnmore is just a push/carry to the plateau then mostly rideable.
The stalker's track out to Poolewe is OK but again water bars.
Torridon descent - very technical but even walking it doesn't take long.
Glen Ling - annoying because there's an obviously easy track on the other side of the river. Make sure you get the right path to find the gate in the deer fence.
Glen Licht, big hike-a-bike to get to Camban bothy
Kinlochleven descent
Devil's Staircase, up and down.
I think I've got your email Ray, I'll send you a document
