I was going to suggest going up to Bwlch tryfan again, but from the other side taking in that quite decent hut circle http://www.themodernantiquarian.com/site/14332/gwern_gof_isaf.html whilst watching Tryfan go by.
Then to the scree path on the left to the "up"
Then to llyn Idawl via the higher Glyder, and then cutting away right from the path to the car, or there abouts.

Could be nice
Charging camera battery now