Frogsisland I'm almost tempted to come with you - just depends on what I can get done Saturday.
I usually start at Llanarmon and come out at Llandrillo but it can be done either way - there are 2 exits/entrances and you takes your choice with either.
But if you start in llanarmon and exit at Llandrillo you gets the choice of another lane nearish that will bring you out above Llangynog.
best to buy the relevant maps and start from there, my experience locally ( I live in Montgomeryshire) is that if your driving and are just a bit out and not acting the **** most people are happy to correct you and send you on your way - the trouble starts with those who want to start the dick swinging contests - remember YOU are the visitor they have to live there and are usually trying to work, so get out of the way of the farm boys - be nice, you never know they may tell you other routes - it does happen.