That route is the one Dave did for his Guinness record (“there and back” hence the Hobbit’s Tale). He got as far as Llyn Brianne on the way back and fell asleep. But he did finish after a bit of a kip. It is a better route, you would follow the “back” route for the classic Carenarfon Castle to the Celtic Ring in Cardiff bay, so the Taff Trail on the way back.
Here is the earlier version of the one-way C2C:
https://drive.google.com/file/d/0B_4N37ty5kpsSl9Yd2x3OVpRM00/view?usp=sharing
But not sure whether there is an official one, Matt Page did the Hobbit version North-South I think and has the record for that (can’t remember what, but under 24h I think).