Totally missed this reply. The 50s examination was typographically based with I think is the frances lynch one. It gets ripped apart in the 70s (?) one. I'll dig out the refs, cant recall off the top of hy head. The circle being / not being earth fast is an interesting q, the grass is always much higher even in the depths of winter so I've not been up to explicitly try and find them.

Waiting for a high def lidar to become available atm to confirm the mound.