From an engineering perspective the angle at the trans and at the pinion should parallel each other and the appropiate degrees of upward movement should be subtracted at the pinion and the pinion be set at that angle.The driveshaft angle will mimic the angle of the trans output shaft in relation to the pinion shaft.Once you establish this angle corrections should be made to insure you are within u-joint opperating range and not at any bind,then you can set the pinion angle for your type of suspension application.You can adjust operating range and parallel the front and back joints by raising and lowering the trans mount or tilting the rearend housing by bar adjustments,pad shims,or welded pad locations,these methods are also used for final pinion settings.
I must agree with Monte that the best setup is to minimise or eliminate any angle except what is necessary for making the joints even under load.With most cars you have to deal with where the trans and rearend are located and do the best under those circumstances,but when building a car,build with the best alignment possible,which is a straight drive train under load.