Should project north be set to true north or magnetic north...I'm assuming it would be true north in order to calculate correct sun angles. Thanks in advanced
It's preferable to set your building orthogonally on the plan. And set North rotation. While calculating sun angle ArchiCAD will use information about north rotation.
True north gives some troubles - as you need to keep your view always rotated. It might lead to not precise angles between walls (i.e. 98.25 degrees or something like that) because of inaccuracy of drafter, problem using cutting planes, saving library parts from plan, placing details and copy lines for new symbol fills.