Shah8,
350 meter altitude will not have much influence, just for 'elevation above sea level' stand point.
However it may mean a particular place where the tree gets direct maximum sun hours, full aeration of the productive branches, i.e. good air circulation (very important), etc..
70 gram for a Negronne breba is very good and quite above the average in the Med places where it is between 40 gr and 60 gr average.
Francisco