Print quality will more be influenced by the pixel dimensions as by the bucket size and raytrace depth. If you are happy with the picture you can see on your screen you already have a good setting. For a print you need to calculate depending on the Dot Per Inch (DPI) the size of your render. An A4 printed with 300 DPI needs a size of 2480 x 3508 and for an A3 you should use 4960 x 7016. If you want 600DPI you need to double those values. Hope this helps Jacques