For god sake do Loop 2 at Penmachno! Did loop 1 also but aprt from a couple of sections, Loop 2 is better IMO.
Spent last week in a cottage about 100m below the end of the second singletrack section after crossing the tarmac road. The way down from it involved a short but oh so sweet 'cheeky' trail too.
We rode it 3 times as well as doing an awesome 'wild' ride from Treifw (Sp?) via Lynn Crafnant, down to Capel Curig and back over the top via Lynn Colywn (Sp?)!
Didn't do the Marin trail, we'll save that for next time.