With respect to BCM permanent, the outline of the route looks splendid (I am assuming it runs clockwise)... Is it possible to do it with GPS validation? (I do understand the risks involved in relying on an electronic device for a 600). Also, is it possible to start/finish in Dolgellau? Seems to make sense in order to reduce the load on the bike
Your post has sparked my interest in doing this. Obviously your experiences this May have inspired you to revisit those roads. I have sketched out a RwGPS route:
https://ridewithgps.com/routes/28456378 Note the 'direct' route back (via Hay) to Chepstow - links to your BCM comments in May.
On enquiry, Black Sheep has recently said: "The perm MR11 . . . route . . . controls used . . . (from a Chepstow depart/arrivee) are Usk, Rhayader, Borth, Barmouth, Caernarfon, Menai Bridge, Llanberis, Betws-y-coed, Dolgellau, Newtown, Llandrindod Wells, Hay-on-Wye, Monmouth.
The route can be ridden either direction." And he separately recognises/implies that riders can start from anywhere (as normal for a permanent - but from Devon, I would go from Chepstow). Why not ask Black Sheep directly - link on the AUK page:
http://www.aukweb.net/perms/detail/MR11/ETA: "is it possible to start/finish in Dolgellau?" Possible, but the Snowdonia loop is only 180k and the loop SSE to Chepstow and back is 420k (which be too long for most).