There is a plan of the sett/shafts in Cornwall Studies Library in their "map drawer" (ask). Failing that, it's in Hamilton Jenkins Mines and Miners, Vol 3.
There is a shaft marker in the park and apart from that, the only evidence recorded by ham jenks of a shaft was at the N side of Sparnon hill, right at the bottom. There is a gap between the wall which is where it would have been. I have not had the balls to investigate this as it's pretty much in someone's garden.
Legend has it one of the manholes in the falmouth road drops into the adit. I'm not sure which one.
The rock was cheese and one of my chums dropped one (whim shaft in the park? ) when it was open and it was 200ft to nothing.
If you find anything else out, I'd be interested, as I'm up the road.
As an interesting point, on the strike of one of the pednandrea lodes, there were "snags" with subsidence where a load of houses got condemned. In line with this, on the lanner road, right by the St Day roundabout is an interesting wall subsidence, I've noted....I wonder if it's shallow stuff on the move.