Thanks for the reply Rhiannon, and you could be onto something. I/ve listed all the thoughts that came to me,but theres bound to be more to it than i can see.
The more i look at the stone the more geometrical it seems to be, but i/m stumped for ideas now. Maybe theres an astronomer out there who can shed some light on it.
One more thing, theres what could have been a cairn on the skyline from maen llia that matches the rising point of the midsummer sun.