Head past Aber falls and go up the hill on the right to more or less between Bera Mawr and Bera Bach. Then cut the side of Garnedd Uchaf.
You come into ogwen down the tarmac track from Llugwy res. Go east on the a5 for 100yds or so (marked) then down south over the river and follow big track back west to the campsite at Gwern Gof Isaf. Then head up the right bank of the stream up past a small lake between Glyder Fach and Foel Goch. There is a small trod after a while on the right hand side of the shallow valley as you climb. Head straight over the col, past a check point and pick up the big track down towards Pen y Gwryd. Leave this track at a wall corner and find a small trod that takes you across south of the lake and drop down to Pen y pass.
Well worth a recce. Try going up Pen Yr Ole Wen, Carnedd Dafydd, Llugwy res, ogwen, up as described above and finish over the Glyders. A great day out.
The race is a great outing. Take it easy on the first half. The pyg track seems like a long way.