Dear me there’s some right snowflakes on here. Nearly got hypothermia in July? If thats true (and I doubt it is) then thats 100% the fault of the person not being properly prepared. And nothing to do with the trail itself.
Don’t let this nonsense influence you in anyway.
I’ve ridden it in every season and like anywhere if you go unprepared you can get caught out. Shock horror and a huge surprise! A ride into the welsh wilderness in the mountains isn’t all sunshine and cocktails and you got wet. Boo hoo.
Also, anyone telling you the Marin is better than Penmachno is absolutely bonkers. I would ride PenMachno and if you still want to do the Marin do the first climb and then go straight down the last descent which is on your right. Don’t waste your time pedalling around the rest of it, the last trail is the only one worth doing and is very good. The rest is utterly pointless if you’re looking for good trails. Probably the most over rated trail i’ve ever ridden.