How to Instal a new French drain (Ed. )

[renishawphil]

I have done French drains at my previous property but no working on a property with a retaining wall which needs a French drain to the fore of it to take away the water from this area
However i am not sure if this time i should go with either fully perforated or semi perforated and is 4 inch pipe big enough, or should i go the whole hog and lay two side by side