Yes, you've got the right spot... south of Trethurgy. Apologies if my grid ref's out. Google Earth (free version) shows a long shadow in that field, the telegraph pole in my photos, with grey blob alongside, but there's not enough definition for me to make the Menear out distinctly. This makes it at grid ref': 50 21' 26.7" N, 04 45' 51.22"W

You're definitely correct about erroneous grid ref's in 'RoTs'...I've come across a number of similar errors in said volume, finding one of the axis usually correct and the other from another site somewhere in the same couple of pages. Has made it more interesting & rewarding finding certain places. Only twigged to this stone, which is very local to me, by having a scan thru' RoTs again, researching another project. Passing the farm in the past I'd speculated around the name, never found anything on the maps and so not ground to scouting it out properly. Duh!

And the view as you look across the valley has St Austell Bay to your right looking over towards Penpillick, with the Eden site at Bodelva below you .

Sorry to set the feline in the aviary!! :) Will try for better images when dry next week .