Hi,
I'm afraid that RailClone does not currently have an equivalent to Forest Pack's Limit to Visibility features. This is because the position of segments in RailClone is always dependent upon their position within the array, so it is always necessary to build the entire array to calculate the position of each segment correctly.
That said, the Stadium tutorial should not be causing such problems and was created and rendered on a machine with a much lower spec than yours. Are you able to open and render the completed scenes from the tutorial downloads?
Many thanks,
Paul