Granite cobble sett depth - 100mm or 50mm

[seanandruby]

Thanks for the reply.
I would only have two cars on the drive, I don't think weight will be too much of an issue, I've put 5 tonne manhole covers in.

Are they the plastic ones? If so they are only good for 5 ton if laid on a plinth too spread the loading, otherwise they will only take 1.5 ton point load on raiser. Assuming it is a plastic I C ?